x^2(x^2+4x+4)=(5x)^2+100x+100

x^2(x^2+4x+4)-25(x^2+4x+4)=0
(x^2-25)×(x^2+4x+4)=0
(x-5)×(x+5)×(x+2)^2=0
x-5=0
x+5=0
(x+2)^2=0
x1=5
x2=-5
x3=-2