1)
а)(8+a)²=64+16a+a²
б)(11-y)²=121-22y+y²
в)(3x-4)²=9x²-24x+16
2)
а)(5x+7y)²-70xy=25x²+70xy+49y²-70xy=25x²+49y²
б)9y²-(x-3y)²=9y²-(x²-6xy+9y²)=9y²-x²+6xy-9y²=6xy-x²=x(6y-x)
в)(5+x)²+x(x-7)=25+10x+x²+x²-7x=2x²+3x+25
г) y(y+7)-(1-y)²=y²+7y-(1-2y+y²)=y²+7y-1+2y-y²=9y-1