a) (3a ²-8bc) ²+4a ²(2c+3b) ²
=(3a ²-8bc) ² - [(2a×(2c - 3b)]²
=[(3-8bc - 2a×(2c - 3b)]×[(3a-8bc + 2a(2c-3b)]
=(3a - 8bc - 4ac + 6ab)×(3a - 8bc + 4ac - 6ab)
b)x(x ²-y ²-z ²)+y(y ²-z ²-x ²)
= y²(x-z) + xz(x-z) - y(x²-z²)
= y²(x-z) + xz(x-z) - y(x-z)(x+z)
= (x-z) (y²+xz-xy-yz)
= (x-z) [z(x-y)- y(x-y)]
= (x-z)(x-y)(z-y)
5 sao nha ông ngủ ik