Quadratic equation of (x^2-4)^2-(x^2-4)-30=0
what about it ?
If you are solving, let y = x^2 - 4
then you have
y^2 - y - 30 = 0
(y-6)(y+5) = 0
y = 6 or y = -5
sub back in:
case1:
x^2 - 4 = 6
x^2 = 10
x = ± √10
case2:
x^2 - 4 = -5
x^2 = -1
x = ± i , if you want complex number solutions.