1)81-(х+2)^2 2)2х^2-4ху+2у^2 3)2х+х^2+2у-у^2
1) 81-(x+2)^2=(7-x)(11+x) 2)2x^2-4xy+2x^2=2(x-y)^2 3)2x+x^2+2y-y^2=(2+x-y)(x+y)