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# How to find a quadratic equation given the solution??

Posted 9 years ago
 We are working on quadratic equations. How would I enter x=4/5,x=3,x=-3 and get the equation?? or a=sqrt10,a=-sqrt10n and get the equation? or x=(-1+_1i)/2 and get the equation? I'm stummped!! Wolfram has been a nightmare on getting simple algebra help. thank you for any help !
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Posted 9 years ago
 It's really sad how I have tried to use wolfram alpha and rarely get correct answers. I started using other sites and got the answers. I tried to come back for this type of equation but can't find the help anywhere. Thank you again and have a great night. Ambi J
Posted 9 years ago
 My mistake, I wrote Sqrt rather than Sqrt ;-) So I should have written (x-Sqrt)(x+Sqrt) I just edited my original post to correct this....I do not believe that there is a way to enter the plus/minus character into Wolfram|Alpha. But when, in algebra, one uses that character it is just a shorthand for writing both cases. I also note that one would hope that Wolfram|Alpha would give the answer to the statement quadratic equation with roots 3 and 9 and give 27 - 12 x + x^2 as the result. But apparently the Wolfram|Alpha parser does note recognize this. I sent in a suggestion that it should address this case.
Posted 9 years ago
 Ok, when I enter the equation in wolfram I don't get the right answer which is a^2-10=0 . I also cant figure out how to enter x=-1(plus or minus)1i /2 do you know if it will calculate that?I so appreciate your help David !
Posted 9 years ago
 If a quadratic equation has two roots --let's call them x1 and x2--then the equation is proportional to (x-x1)(x-x2) In your example x1 = Sqrt x2 = -Sqrt so the equaiton is (x-Sqrt)(x+Sqrt) you can expand this out to get the equivalent x^2 - 10 
Posted 9 years ago
 Just enter the equation: (x-a)(x-b) where a and b are the two roots. That, of course, is the quadratic equation with those roots
Posted 9 years ago
 I'm sorry but i didn't understand your answer. I have the solution I need the equation from the solution.do you know how to enter where the plus is over the minus for "plus or minus"so sorry but I may have not asked the question right. Here is an example : a=sqrt10, a= - sqrt10 what is the solution to this ?Thank you !!