2016-01-18 13:43:16 +0100 received badge ● Student (source) 2016-01-18 08:51:02 +0100 received badge ● Popular Question (source) 2012-12-02 05:16:16 +0100 commented question Solve contains wrong solution I know, that I could only solve for f'(x)==0 and filter for f''(x)<0 but solve shouldn't contain solutions like that, I think. 2012-12-02 04:50:28 +0100 commented answer Solve contains wrong solution surely there must be something slightly off with this solution because for x=1 y is always 0. Only the local maximum at (t - 2)/t changes. 2012-12-01 22:14:02 +0100 asked a question Solve contains wrong solution Hello, I tried to following to find a maxima of a function: var('t x'); f=(e^(x*t))*(x-1)^2; maxima = solve([derivative(f,x)==0, derivative(f,x,2)<0],x) show(maxima);  And the solution sage spits out are: [ [x == 1, -2 > 0], [x == (t - 2)/t, -(t - 2)^2 + 2*(t - 2)*t - t^2 + 6 > 0] ]  I understand that sage cannot evaluate the validity of the second solution but the first one surely is no solution at all. Why does it give me this solution or am I doing anything wrong?