x²-y²=(x-y)(x+y)
y²-x²=(y-x)(y+x)
a²-9=(a-3)(a+3)
16-b²=(4-b)(4+b)
a)(x-y)*(x+y)
б)(y-x)*(y+x)
в)(a-3)*(a+3)
г)(4-b)*(4+b)
