Question

(у-3)(у+3)-у(у+7)
а(а-8)+(5-а)(а+5)
(5m-n)(5m+n)+2m(m-n)
2x(x+y)-(2x+y)(2x-y)

Answer 1

(у-3)(у+3)-у(у+7)=y²-9-y²-7x=-9-7y

а(а-8)+(5-а)(а+5)=a²-8a+25-a²=25-8a

(5m-n)(5m+n)+2m(m-n)=25m²-n²+2m²-2mn=27m²-2mn-n²

2x(x+y)-(2x+y)(2x-y)=2x²+2xy-(4x²-y²)=2x²+2xy-4x²+y²=y²+2xy-2x²