maths question (1 Viewer)

[vizman]

hey guys,

i seem to be stuck on this question

"find the cubic equation whose roots are the squares of that of x^3 + 2x + 1 = 0"

i seem to keep getting x^3 - 4x^2 + 1

any ideas?

ta.

 

[klaw]

Let a, b and c be the roots of x^3 + 2x + 1 = 0
Let x=a^2
a=sqrt(x)
Since a is a root, then it must satisfy the equ

.:sqrt(x)^3+2sqrt(x)+1=0
sqrt(x)(2+x)^2=-1
x(4+4x+x^2)=1
.: x^3+4x^2+4x-1=0 is the required equ