1-(x^2-2xy+y^2)
1-a^2-2ab-b^2
4+(-x^2-2xy-y^2)

1-(x²-2xy+у²)=1-(х-у)²=(1-(х-у))(1+(х-у))=(1-х+у)(1+х-у)

1-а²-2ab-b²=1-(а²+2ab+b²)=1-(a+b)²=(1-(a+b))(1+(a+b))=(1-a-b)(1+a+b)

4+(-x²-2xy-y²)=4-х²-2ху-у²=4-(х²+2ху+у²)=4-(х+у)²=(2-(х+у))(2+(х+у))=(2-х-у)(2+х+у)