(а^2+4) ^2 - 16а^2 = (а+2)^2 *(а-2)^2

Question

(а^2+4) ^2 - 16а^2 = (а+2)^2 *(а-2)^2

Answer 1

a^4+8a^2+16-16a^2=(a^2+(4a+4))(a^2-(4a+4))

a^4-8a^2+16=(a^2)^2-(4a+4)^2

a^4-8a^2+16=a^4-16a^2-32a-16

-8a^2+16+16a^2+32a+16=0

8a^2+32a+32=0

a^2+4a+4=0

(a+2)^2=0

a+2=0

a=-2