Community RSS Feed https://community.wolfram.com RSS Feed for Wolfram Community showing any discussions in tag Algebra sorted by active Unexpected results from Solve[ ]? https://community.wolfram.com/groups/-/m/t/2250180 Hi I am having some troubles using Solve. Specifically, I want to determine the intercept curve of two surfaces. I have two functions wh[n_, B_] and wh1[n, B], these functions are equal for n=10^5 and B=0.32. Nevertheless, when I set B=0.32 and I use Solve to calcule the intercept point, Solve doesn’t work properly, It shows an imaginary result when It should give n=10^5. Finally, in others examples the result of Solve is { }. Would you help me with these two problems? Thank you in advance. &amp;[Wolfram Notebook] : https://www.wolframcloud.com/obj/73f2bd89-d042-4efa-b88a-fc713e476ba2 Benny Rodríguez Saenz 2021-04-22T05:56:04Z Matrix representation of a central finite difference scheme. https://community.wolfram.com/groups/-/m/t/2250341 I am struggling to write a code for a central finite difference scheme in Mathematica. I need assistance identifying books, sites or videos that can get me started. Sam Rametse 2021-04-22T11:56:21Z Inconsistent results for inequality query https://community.wolfram.com/groups/-/m/t/2249279 Hi All, I&#039;ve been trying to have Wolfram|Alpha help me out with some inequality calculations, but I can&#039;t seem to get consistent results. Here is an example. I&#039;m looking for values that will give certain errors in this series, and when I use the variable n, I do get a list of possible values that meet the inequality: ![enter image description here] Wanting a precise value, and thinking that the choice of variable may have had something to do with it, I put in x, however the answer is then wildly inaccurate (real answer 4&lt;x&lt;5 somewhere): ![enter image description here] What could be happening here? : https://community.wolfram.com//c/portal/getImageAttachment?filename=icr_1.png&amp;userId=2248809 : https://community.wolfram.com//c/portal/getImageAttachment?filename=icr_2.png&amp;userId=2248809 Shaun Olafson 2021-04-21T05:34:48Z NMinimize not working on custom function? https://community.wolfram.com/groups/-/m/t/2248727 When defining the values of suma[x] as regression function I &#039;m able to obtain te true values of suma[x], when entering x manually. Nevertheless when I try to Nminimize suma[x] it seems that this finction does not take the value of x I willl thank a lot any suggestion Thanks &amp;[Wolfram Notebook] : https://www.wolframcloud.com/obj/3d03f9cc-d6fe-475f-bf32-262c139733c0 rafael ibanez 2021-04-20T16:52:27Z Represent and compute with matrix-valued functions of a vector? https://community.wolfram.com/groups/-/m/t/2247942 In the attachment I pose a problem of representing and computing with a matrix-valued function of a vector. Before I go to the effort of learning Mathematica, I would like to know that it can do these kinds of computations and yield results in the usual notation or something close to it. I would appreciate any guidance, including being told that my request is impossible. Thanks. Darwin Poritz 2021-04-19T21:33:03Z Looking for a closed-form solution using Solve[ ] https://community.wolfram.com/groups/-/m/t/2246994 I was wondering if a closed form solution does exist for the following equation: a^2 Exp[x/a] + x^2/2 (1 - b) - a^2 - a x Exp[x/a] = 0 where a and b are Real numbers. I would like to obtain a solution of the form x=f(a,b). I tried to use the following command: Solve[a^2*Exp[x/a] + x^2/2*(1 - b) - a^2 - a*x*Exp[x/a] == 0, x, Assumptions -&gt; Element[a, Reals], Assumptions -&gt; Element[b, Reals]] but I obtained the following message: Solve: This system cannot be solved with the methods available to Solve. I was wondering whether I could use the Lambert W function to solve this equation or if there is any way to obtain an approximated solution of this equation. I am looking for a solution for x&lt;0, and I know that a&gt;0, if this can make any difference. Thank you. **Edited after the 1st reply:** The last sentence is probably superfluous: I am interested in the general closed-form solution of this equation. Then, I will use the part of solution when x&lt;0 (which happens when 0&lt;b&lt;1). sebastiano piccolroaz 2021-04-19T08:13:21Z