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# won't evaluate answers given by solve()

asked 2016-09-12 22:40:58 +0200 This post is a wiki. Anyone with karma >750 is welcome to improve it.

I am solving an equation and then trying to plug in the answers it gives to show that the answers are correct, but sage will not evaluate the answers i plug in.

solve(x^3+1==0,x)


yields

[x == 1/2*I*sqrt(3)*(-1)^(1/3) - 1/2*(-1)^(1/3),
x == -1/2*I*sqrt(3)*(-1)^(1/3) - 1/2*(-1)^(1/3),
x == (-1)^(1/3)]


if you then put into sage (1/2*I*sqrt(3)*(-1)^(1/3) - 1/2*(-1)^(1/3))^3+1 the result it gives is (1/2*I*sqrt(3)*(-1)^(1/3) - 1/2*(-1)^(1/3))^3 + 1. it's like it doesn't know what to do with it's own answers.

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## 1 Answer

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You will need to ask it to simplify.

soln=solve(x^3+1==0,x)
soln
f(x) = x^3+1
for s in soln:
f(s.rhs()).simplify_full()

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Asked: 2016-09-12 22:40:58 +0200

Seen: 107 times

Last updated: Sep 13 '16