А)(y-4)²б)(7x+a)²в)(в+3)(в-3)г)(5у-2х)(5у+2х)
а)(y-4)²=(y)²-2*y*4+(4)²=y²-8y+16
б)(7x+a)²=(7x)²+2*7x*a+(a)²=49x²+14ax+a²
в)(b+3)(b-3)=(b)²-(3)²=b²-9
г)(5y-2x)(5y+2x)=(5y)²-(2x)²=25y²-4x²