Question

How many solutions does this equation have x^4 - 6x^2 -7 = 0

Answer 1

2 solutions

Explanation:

x^4-6x^2-7=0

Replace x^2 by y

(x^2)^2-6x^2-7=0

y^2-6y-7=0

D=b^2-4ac= (-6)^2-4*1*(-7)= 36+28=64

sqrtD=8

y1=(-b-sqrtD)/2a=-2/2=-1

y2= (-b+sqrtD)/2a=14/2=7

x^2=-1(n0 roots) x^2=7 x=sqrt7 or x=-sqrt7

2 roots