Ответ:

(х-у)(х+у)=х²-y²

(2-x)(x+2)=4-x²

(2х+1)(1-2х)=1-4х²

(2х-у)(2х+у)=4х²-у²

(2х+3у)(3у-2х)=9у²-4х²

(х²-2)(2+х²)=х^4 -4

(3х²-0,2у²)(0.2у+3х²)=9х^4.-0.04

всі крім ост.)