# \#equation-solving **URL:** https://community.wolfram.com/tag/equation-solving/44.md [Latest](https://community.wolfram.com/latest.md) · [Categories](https://community.wolfram.com/categories.md) · [Tags](https://community.wolfram.com/tags.md) --- ## [On the message "Equations may not give solutions for 'all' variables"](https://community.wolfram.com/t/on-the-message-equations-may-not-give-solutions-for-all-variables/28377)
**Author:** [@HyungKyuKim](https://community.wolfram.com/u/HyungKyuKim)\ **Replies:** 9\ **Last updated:** [October 27, 2026, 1:51am UTC](https://community.wolfram.com/t/on-the-message-equations-may-not-give-solutions-for-all-variables/28377 "2026-10-27T01:51:31Z")
I tried to solve a simultaneous equation consists of numeric coefficients and a paramater (say, ‘xi’). I got the message shown in the title when the matrix size of the coefficient exceeds 6. Up to 5, the “Solve” gave the… --- ## [Algebraic Hirota construction of one- and two-soliton solutions of the DNLS equation and their Bohmian trajectories](https://community.wolfram.com/t/algebraic-hirota-construction-of-one-and-two-soliton-solutions-of-the-dnls-equation-and-their-bohmian-trajectories/28298)
**Author:** [@kvbloh](https://community.wolfram.com/u/kvbloh)\ **Replies:** 1\ **Last updated:** [October 9, 2026, 8:01pm UTC](https://community.wolfram.com/t/algebraic-hirota-construction-of-one-and-two-soliton-solutions-of-the-dnls-equation-and-their-bohmian-trajectories/28298 "2026-10-09T20:01:21Z")
Open in Wolfram Cloud ↗ DOWNLOAD-DESKTOP-NOTEBOOK.nb (10.8 MB) --- ## [Fixing Reduce\[ForAll\[…\]\]: a quantifier-syntax pitfall](https://community.wolfram.com/t/fixing-reduce-forall-a-quantifier-syntax-pitfall/28184)
**Author:** [@camelon](https://community.wolfram.com/u/camelon)\ **Replies:** 1\ **Last updated:** [September 27, 2026, 6:54pm UTC](https://community.wolfram.com/t/fixing-reduce-forall-a-quantifier-syntax-pitfall/28184 "2026-09-27T18:54:35Z")
Why can’t we solve this identity for the values of a, b, t? Reduce\[ForAll\[{x, y}, {x \> 0, y \> 0, t \> 0, t^2 + 2 t x + x^2 + 2 t y + 12 + y^2 == a^2 + b^2 - 2 a x + x^2 - 2 b y + y^2}\], {a, b, t}, Reals\] Reduce\[ForAll\[{… --- ## [The hidden geometry of Hopf: how the prey nullcline decides where oscillations can be born](https://community.wolfram.com/t/the-hidden-geometry-of-hopf-how-the-prey-nullcline-decides-where-oscillations-can-be-born/28174)
**Author:** [@eduardoclopez13](https://community.wolfram.com/u/eduardoclopez13)\ **Replies:** 1\ **Last updated:** [September 25, 2026, 4:51pm UTC](https://community.wolfram.com/t/the-hidden-geometry-of-hopf-how-the-prey-nullcline-decides-where-oscillations-can-be-born/28174 "2026-09-25T16:51:42Z")
Open in Wolfram Cloud ↗ DOWNLOAD-DESKTOP-NOTEBOOK.nb (8.2 MB) --- ## [How to make NDSolve solve this apparently easy DE system?](https://community.wolfram.com/t/how-to-make-ndsolve-solve-this-apparently-easy-de-system/28084)
**Author:** [@nbbienia](https://community.wolfram.com/u/nbbienia)\ **Replies:** 8\ **Last updated:** [September 23, 2026, 9:01am UTC](https://community.wolfram.com/t/how-to-make-ndsolve-solve-this-apparently-easy-de-system/28084 "2026-09-23T09:01:10Z")
Hello, I have been trying to solve a BVP for a system of two apparently easy DEs, by using the code: k=7; (OK) (k=8; fails )g=1; d=1; sol=NDSolve\[{u''\[x\]-ku\[x\]/(g+u\[x\])==0,v''\[x\]+ku\[x\]/(g+u\[x\])/d==0,u'\[0\]==0,u\[1\]==1,… --- ## [Is my new mean for elementary asymmetric functions with singularities existent and non-equivalent to their Cauchy Principal Value?](https://community.wolfram.com/t/is-my-new-mean-for-elementary-asymmetric-functions-with-singularities-existent-and-non-equivalent-to-their-cauchy-principal-value/28077)
**Author:** [@bharathk98](https://community.wolfram.com/u/bharathk98)\ **Replies:** 3\ **Last updated:** [September 22, 2026, 7:24pm UTC](https://community.wolfram.com/t/is-my-new-mean-for-elementary-asymmetric-functions-with-singularities-existent-and-non-equivalent-to-their-cauchy-principal-value/28077 "2026-09-22T19:24:42Z")
Motivations First Motivation: I got a “new mean” by indirectly attempting to establish the relationship between the uniform probability measure and normalized Hausdorff measure. This is the third open problem in Section … --- ## [Finding all global minima with IPOPT (Interior Point OPTimizer)](https://community.wolfram.com/t/finding-all-global-minima-with-ipopt-interior-point-optimizer/27513)
**Author:** [@fkampas](https://community.wolfram.com/u/fkampas)\ **Replies:** 1\ **Last updated:** [September 2, 2026, 6:26pm UTC](https://community.wolfram.com/t/finding-all-global-minima-with-ipopt-interior-point-optimizer/27513 "2026-09-02T18:26:08Z")
Open in Wolfram Cloud ↗ DOWNLOAD-DESKTOP-NOTEBOOK.nb (103 KB) --- ## [How do you calculate the magnitude of this vector?](https://community.wolfram.com/t/how-do-you-calculate-the-magnitude-of-this-vector/27476)
**Author:** [@matlabes](https://community.wolfram.com/u/matlabes)\ **Replies:** 1\ **Last updated:** [August 24, 2026, 1:47pm UTC](https://community.wolfram.com/t/how-do-you-calculate-the-magnitude-of-this-vector/27476 "2026-08-24T13:47:57Z")
Reduce\[{Norm\[a\] == Norm\[b\] == Norm\[c\]==2, VectorAngle\[a, b\] == \[Pi\]/3, VectorAngle\[a, c\] == \[Pi\]/3, VectorAngle\[b, c\] == \[Pi\]/2, t == Norm\[3 a/2 + b/2 + 3 c/2\]}, t\] Given the magnitudes of each vector and the angles b… --- ## [Syntax error using RecurrenceTable function simulatin Stock-Flow Consistent model](https://community.wolfram.com/t/syntax-error-using-recurrencetable-function-simulatin-stock-flow-consistent-model/27405)
**Author:** [@winkllj](https://community.wolfram.com/u/winkllj)\ **Replies:** 9\ **Last updated:** [August 23, 2026, 7:20pm UTC](https://community.wolfram.com/t/syntax-error-using-recurrencetable-function-simulatin-stock-flow-consistent-model/27405 "2026-08-23T19:20:27Z")
See attached NB. A manipulate module using the RecurrenceTable function detects a syntax error which I have been unable to see. More eyes on what might be obvious to others might help. Open in Wolfr… --- ## [Solve this mixed partial differential equation](https://community.wolfram.com/t/solve-this-mixed-partial-differential-equation/16128)
**Author:** [@xiang33](https://community.wolfram.com/u/xiang33)\ **Replies:** 5\ **Last updated:** [August 15, 2026, 3:42pm UTC](https://community.wolfram.com/t/solve-this-mixed-partial-differential-equation/16128 "2026-08-15T15:42:36Z")
This is my QS: This is my Code: Open in Wolfram Cloud ↗ --- ## [Hirota multi-soliton solutions of the resonant nonlinear Schrödinger equation & Bohmian dynamics](https://community.wolfram.com/t/hirota-multi-soliton-solutions-of-the-resonant-nonlinear-schrodinger-equation-bohmian-dynamics/27444)
**Author:** [@kvbloh](https://community.wolfram.com/u/kvbloh)\ **Replies:** 1\ **Last updated:** [August 13, 2026, 2:19pm UTC](https://community.wolfram.com/t/hirota-multi-soliton-solutions-of-the-resonant-nonlinear-schrodinger-equation-bohmian-dynamics/27444 "2026-08-13T14:19:01Z")
Open in Wolfram Cloud ↗ DOWNLOAD-DESKTOP-NOTEBOOK.nb (9.17 MB) --- ## [Ramanujan's number: finding sum of two positive cubes](https://community.wolfram.com/t/ramanujans-number-finding-sum-of-two-positive-cubes/27430)
**Author:** [@fkampas](https://community.wolfram.com/u/fkampas)\ **Replies:** 3\ **Last updated:** [August 12, 2026, 9:27pm UTC](https://community.wolfram.com/t/ramanujans-number-finding-sum-of-two-positive-cubes/27430 "2026-08-12T21:27:18Z")
fi = FindInstance\[{a^3 + b^3 == c^3 + d^3, a != c, a != d}, {a, b, c, d}, PositiveIntegers\] {{a -\> 10, b -\> 9, c -\> 12, d -\> 1}} {a^3 + b^3, c^3 + d^3} /. fi {{1729, 1729}} Solve, NSolve and Reduce cannot do this… --- ## [Cannot solve simple equation](https://community.wolfram.com/t/cannot-solve-simple-equation/27439)
**Author:** [@au125806](https://community.wolfram.com/u/au125806)\ **Replies:** 1\ **Last updated:** [August 12, 2026, 1:39pm UTC](https://community.wolfram.com/t/cannot-solve-simple-equation/27439 "2026-08-12T13:39:55Z")
Hello, I am trying to solve a relatively simple differential equation DSolve\[y''\[x\] - ay\[x\] == -b, y\[x\], x\] that I know has a solution (in my notation): y = C1 exp(sqrt(a)\*t) +C2 exp(-sqrt(a)\*t) +b/a. However, Mathe… --- ## [An introduction to the U.T.M: the heat equation on a finite interval](https://community.wolfram.com/t/an-introduction-to-the-u-t-m-the-heat-equation-on-a-finite-interval/27392)
**Author:** [@atparaskevopoulos](https://community.wolfram.com/u/atparaskevopoulos)\ **Replies:** 1\ **Last updated:** [August 6, 2026, 12:42pm UTC](https://community.wolfram.com/t/an-introduction-to-the-u-t-m-the-heat-equation-on-a-finite-interval/27392 "2026-08-06T12:42:37Z")
Open in Wolfram Cloud ↗ DOWNLOAD-DESKTOP-NOTEBOOK.nb (244 KB) --- ## [Mathmatica pefromance and CPU usage in equation solving](https://community.wolfram.com/t/mathmatica-pefromance-and-cpu-usage-in-equation-solving/23752)
**Author:** [@nima](https://community.wolfram.com/u/nima)\ **Replies:** 4\ **Last updated:** [August 5, 2026, 1:05am UTC](https://community.wolfram.com/t/mathmatica-pefromance-and-cpu-usage-in-equation-solving/23752 "2026-08-05T01:05:12Z")
I have a general question that may have been addressed previously, albeit not directly. I utilize Mathematica to solve a set of non-linear equations and achieve successful results. However, the computation time is consid… --- ## [\[BOOK\] Exploring Partial Differential Equations: A Computational Approach now available](https://community.wolfram.com/t/book-exploring-partial-differential-equations-a-computational-approach-now-available/27399)
**Author:** [@aramm](https://community.wolfram.com/u/aramm)\ **Replies:** 1\ **Last updated:** [August 3, 2026, 3:37pm UTC](https://community.wolfram.com/t/book-exploring-partial-differential-equations-a-computational-approach-now-available/27399 "2026-08-03T15:37:50Z")
Open in Wolfram Cloud ↗ DOWNLOAD-DESKTOP-NOTEBOOK\_Updated\_by\_aramm.nb (1.94 MB) --- ## [Jacobian conjecture counterexample by LLM](https://community.wolfram.com/t/jacobian-conjecture-counterexample-by-llm/27349)
**Author:** [@antononcube](https://community.wolfram.com/u/antononcube)\ **Replies:** 4\ **Last updated:** [July 26, 2026, 2:52pm UTC](https://community.wolfram.com/t/jacobian-conjecture-counterexample-by-llm/27349 "2026-07-26T14:52:15Z")
Open in Wolfram Cloud ↗ DOWNLOAD-DESKTOP-NOTEBOOK.nb (493 KB) --- ## [\[WSRI26\] Interpreting How Neural Nets Regress Cubic Polynomials](https://community.wolfram.com/t/wsri26-interpreting-how-neural-nets-regress-cubic-polynomials/27331)
**Author:** [@enricobottazzi](https://community.wolfram.com/u/enricobottazzi)\ **Replies:** 1\ **Last updated:** [July 18, 2026, 7:08pm UTC](https://community.wolfram.com/t/wsri26-interpreting-how-neural-nets-regress-cubic-polynomials/27331 "2026-07-18T19:08:29Z")
Open in Wolfram Cloud ↗ DOWNLOAD-DESKTOP-NOTEBOOK.nb (6.43 MB) --- ## [Function\[\] not returning a function I can call](https://community.wolfram.com/t/function-not-returning-a-function-i-can-call/27299)
**Author:** [@winkllj](https://community.wolfram.com/u/winkllj)\ **Replies:** 2\ **Last updated:** [July 17, 2026, 4:47pm UTC](https://community.wolfram.com/t/function-not-returning-a-function-i-can-call/27299 "2026-07-17T16:47:30Z")
Eventually, I want to solve Stock-Flow Consistent equations of Wynne Godley from his book Monetary Economics. There are already software systems (in R and Python) developed to support those solutions but the solutions re… --- ## [Extending FindInstance](https://community.wolfram.com/t/extending-findinstance/27274)
**Author:** [@fkampas](https://community.wolfram.com/u/fkampas)\ **Replies:** 8\ **Last updated:** [July 15, 2026, 8:21pm UTC](https://community.wolfram.com/t/extending-findinstance/27274 "2026-07-15T20:21:25Z")
Open in Wolfram Cloud ↗ --- ## [\[WSRP26\] Modeling dosing regimens with pharmacokinetic models for personalized glibenclamide therapy](https://community.wolfram.com/t/wsrp26-modeling-dosing-regimens-with-pharmacokinetic-models-for-personalized-glibenclamide-therapy/27261)
**Author:** [@sreejappala](https://community.wolfram.com/u/sreejappala)\ **Replies:** 1\ **Last updated:** [July 11, 2026, 2:03pm UTC](https://community.wolfram.com/t/wsrp26-modeling-dosing-regimens-with-pharmacokinetic-models-for-personalized-glibenclamide-therapy/27261 "2026-07-11T14:03:02Z")
Open in Wolfram Cloud ↗ DOWNLOAD-DESKTOP-NOTEBOOK.nb (1.84 MB) --- ## [How to speed up code for solving complex equations](https://community.wolfram.com/t/how-to-speed-up-code-for-solving-complex-equations/27180)
**Author:** [@matlabes](https://community.wolfram.com/u/matlabes)\ **Replies:** 4\ **Last updated:** [July 9, 2026, 5:11pm UTC](https://community.wolfram.com/t/how-to-speed-up-code-for-solving-complex-equations/27180 "2026-07-09T17:11:47Z")
{pM = {xM, yM, 2}, pD = {0, 0, 0}, pN = {0, 2, h}, pA = {2, 0, 0}, relcir = (xM - 1)^2 + (yM - 1)^2 == 1, pQ = {a, b, c}} slq = Solve\[{pQ - pA == \[Lambda\] (pN - pA)}\]\[1\] pQ = pQ /. slq AbsoluteTiming@ Reduce\[{Norm\[p… --- ## [Why can't the powerful Reduce and Solve functions handle this type of parametric inequality problem?](https://community.wolfram.com/t/why-cant-the-powerful-reduce-and-solve-functions-handle-this-type-of-parametric-inequality-problem/27179)
**Author:** [@matlabes](https://community.wolfram.com/u/matlabes)\ **Replies:** 4\ **Last updated:** [July 9, 2026, 2:26pm UTC](https://community.wolfram.com/t/why-cant-the-powerful-reduce-and-solve-functions-handle-this-type-of-parametric-inequality-problem/27179 "2026-07-09T14:26:14Z")
Reduce\[{x\> -1, (1 - m + x) (E^x - 1/(1 + x))\>0, 0 \< m \< 1}, x, Reals\] Why can’t the powerful Reduce and Solve functions handle this type of parametric inequality problem? --- ## [Is there a way to solve the eigenvalues of a linear operator without giving its matrix form?](https://community.wolfram.com/t/is-there-a-way-to-solve-the-eigenvalues-of-a-linear-operator-without-giving-its-matrix-form/22872)
**Author:** [@junjunxu87](https://community.wolfram.com/u/junjunxu87)\ **Replies:** 6\ **Last updated:** [July 1, 2026, 11:33pm UTC](https://community.wolfram.com/t/is-there-a-way-to-solve-the-eigenvalues-of-a-linear-operator-without-giving-its-matrix-form/22872 "2026-07-01T23:33:59Z")
In Python or Matlab, the eigensolver can solve the system by giving the linear function (for example, in Matlab we can use eigs(Afun,…)), this speeds up the calculation largely as we do not need to construct the whole ma… --- ## [Why get different results when solving the same complex equation using Reduce and Solve?](https://community.wolfram.com/t/why-get-different-results-when-solving-the-same-complex-equation-using-reduce-and-solve/27096)
**Author:** [@mmamathes](https://community.wolfram.com/u/mmamathes)\ **Replies:** 1\ **Last updated:** [June 22, 2026, 1:01pm UTC](https://community.wolfram.com/t/why-get-different-results-when-solving-the-same-complex-equation-using-reduce-and-solve/27096 "2026-06-22T13:01:09Z")
Reduce\[{Norm\[z1\] == Norm\[z2\] == 2, z1 + z2 == Sqrt\[3\] + I, y == Norm\[z1 - z2\]}, y, {z1, z2}\] Solve\[{Norm\[z1\] == Norm\[z2\] == 2, z1 + z2 == Sqrt\[3\] + I, y == Norm\[z1 - z2\]}\] // FullSimplify Why get different results w… --- ## [Generalized exponential rational function technique for nonlinear partial differential equations](https://community.wolfram.com/t/generalized-exponential-rational-function-technique-for-nonlinear-partial-differential-equations/27067)
**Author:** [@namantaggar](https://community.wolfram.com/u/namantaggar)\ **Replies:** 1\ **Last updated:** [June 16, 2026, 6:01pm UTC](https://community.wolfram.com/t/generalized-exponential-rational-function-technique-for-nonlinear-partial-differential-equations/27067 "2026-06-16T18:01:02Z")
Open in Wolfram Cloud ↗ DOWNLOAD-DESKTOP-NOTEBOOK.nb (781 KB) --- ## [How to solve this type of vector operation problem?](https://community.wolfram.com/t/how-to-solve-this-type-of-vector-operation-problem/27058)
**Author:** [@mmamathes](https://community.wolfram.com/u/mmamathes)\ **Replies:** 3\ **Last updated:** [June 13, 2026, 11:47pm UTC](https://community.wolfram.com/t/how-to-solve-this-type-of-vector-operation-problem/27058 "2026-06-13T23:47:49Z")
Reduce\[{Norm\[a + b\] == 1, Norm\[a - b\] == Sqrt\[3\], t == a . b}, t, {a, b}, Reals\] The code above has been running for a long time without producing an answer. How can this problem be solved using code? --- ## [Resource function for the numerical solution of certain nonlinear integral equations](https://community.wolfram.com/t/resource-function-for-the-numerical-solution-of-certain-nonlinear-integral-equations/25999)
**Author:** [@dangregori](https://community.wolfram.com/u/dangregori)\ **Replies:** 2\ **Last updated:** [June 12, 2026, 7:56pm UTC](https://community.wolfram.com/t/resource-function-for-the-numerical-solution-of-certain-nonlinear-integral-equations/25999 "2026-06-12T19:56:48Z")
Open in Wolfram Cloud ↗ DOWNLOAD-DESKTOP-NOTEBOOK.nb (538 KB) --- ## [DSolve v.s. copilot for Coulomb damping](https://community.wolfram.com/t/dsolve-v-s-copilot-for-coulomb-damping/26483)
**Author:** [@imaruyama](https://community.wolfram.com/u/imaruyama)\ **Replies:** 4\ **Last updated:** [May 28, 2026, 9:05am UTC](https://community.wolfram.com/t/dsolve-v-s-copilot-for-coulomb-damping/26483 "2026-05-28T09:05:47Z")
Recently, I found that Google Copilot can solve a nonlinear but solvable equation like coulomb damping\[1\], just by searching for “r’‘(t)=-r(t)-sgn(r’(t))/10, r(0)=0, r’(0)=1” \[2\], whether Copilot’s time-dependent answer … --- ## [Unexpected result from DSolve? (Version dependence)](https://community.wolfram.com/t/unexpected-result-from-dsolve-version-dependence/24687)
**Author:** [@imaruyama](https://community.wolfram.com/u/imaruyama)\ **Replies:** 8\ **Last updated:** [May 28, 2026, 8:58am UTC](https://community.wolfram.com/t/unexpected-result-from-dsolve-version-dependence/24687 "2026-05-28T08:58:51Z")
Could you help me to understand the following? In\[1\]:= $VersionNumber Out\[1\]= 14. In\[2\]:= DSolve\[{2.3\*r''\[t\]==1-r'\[t\],r\[0\]==0,r'\[0\]==0},r\[t\],t\]//FullSimplify Out\[2\]= {{r\[t\] -\> -2. + 2.3 E^(-0.434783 t)}} In\[3\]:= DSo… [Next page](https://community.wolfram.com/tag/equation-solving/44.md?match_all_tags=true&page=1&tags%5B%5D=equation-solving)