Ta có:
(x2 + y2)2 - 4x2y2 = (x2 + y2)2 - (2xy)2 = (x2 + y2 - 2xy)(x2 + y2 + 2xy) = (x - y)2(x + y)2
(x^2+y^2)^2-4x^2y^2
=x^4+2x^2y^2+y^4-4x^2y^2
=x^4-2x^2y^2+^4
=(x^2-y^2)^2
hok tốt he
Ta có (x2 + y2 )2 -4x2y2 = x4 +y4 + 2x2y2 -4x2y2
= x4 + y4 -2x2y2
= (x2 - y2)2