Answer:

Given that function

(1−y 2 )(1−x 2 )+4xy

⇒1−x 2 −y 2 +x 2 y 2 +4xy

⇒x 2 y 2 +1−x 2 −y 2 +2xy+2xy

⇒x 2 y 2 +1+2xy−(x 2 +y 2 −2xy)

(xy+1) 2 −(x−y) 2

⇒ We know that ∵(a 2 −b 2 )=(a+b)(a−b)

(xy+1+x−y)(xy+1−x+y)

=(xy+x−y+1)(xy+y−x+1)