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Unable to find explicit solution to a very simple equation

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So my code is
syms x
solve(-3*x^4+12*x^2 > 0,x)
And for some reason matlab cant answer this. I have tried everything but nothing has worked so far
the answer should be x=0 and x=+-2, but instead i get
Warning: Unable to find explicit solution. For options, see help.
ans =
Empty sym: 0-by-1
What am i doing wrong? I am losing my mind cause I know this is a very simple task

Accepted Answer

Paul on 15 Sep 2021
Edited: Paul on 15 Sep 2021
The equation in the question is an inequality, but the supposed solution posed in the question is for an equality:
syms x real
f(x) = -3*x^4 + 12*x^2;
ans = 
Plot f(x)
fplot(f(x),[-2 2])
So that gives us an idea of what the solution should be for f(x) > 0.
assume(x,'real') % otherwise the solver will consider x as complex
sol = solve(f(x)>0,'ReturnConditions',true);
ans = 
ans = 
ans = 
Which looks like the expected solution based on the graph.
  1 Comment
Teemu Hämäläinen
Teemu Hämäläinen on 15 Sep 2021
Thanks a million times! I wouldn't have figured it out on my own. It works now! <3

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