-4(x^-8)=84
check you problem, I think you typed it here wrong
what is the exponent, -8 ?
divide each side by -4
multipy both sides by x^8
1=-22 *x^8
taking the 8th root of each side:
1=(-22)^1/8 * x
x= [1/(-22)^1/8 ]
x=0.627787278 - 0.260038005 i
I am wondering if you teacher meant to give you a complex solution.