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#