How do you find the real solutions of the polynomial $x^4+2x^2=15$ ?

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Answer 1 · 2017-05-24T09:51:30

$x=+-sqrt3$

$x^4+2x^2=15$

Let $z=x^2$

$:. z^2+2z-15=0$

$(z+5)(z-3)=0$

$z= -5$ or $+3$

Hence: $x=+-sqrt(-5)$ or $x=+-sqrt3$

The question asks for real solutions only.

$:. x=+-sqrt3$

How do you find the real solutions of the polynomial x^4+2x^2=15x^4+2x^2=15?