Solve (x^2-4x-8)(x^2-4x)=48.

(x^2-4x-8)(x^2-4x)=48
(x^2-4x-8)[(x^2-4x-8)+8]=48
設(x^2-4x-8)=y
y(y+8)=48
y^2+8y-48=0
∴ (y-4)(y+12)=0
y=4 or y=-12
x^2-4x-8=4 or x^2-4x-8=-12
x^2-4x-12=0 or x^2-4x+4=0
∴ (x-6)(x+2)=0 or (x-2)^2=0
x=6, x=-2, or x=2