Answers

2016-04-16T23:25:19+05:30
= (1-x^2)×(1-y^2)+4xy
= 1×(1-y^2)-x^2(1-y^2)+4xy
= 1-y^2-x^2+x^2 y^2 + 4xy
= (1+2xy+ x^2 y^2) - (y^2 + x^2 - 2xy)
= (1+xy)^2 - (x-y)^2
= [(1+xy)+(x-y)] × [( 1+xy)- (x-y)]
= [(1+x-y + xy) ×( 1-x+y + xy)]
0