a) x2 - y2 - 4x + 4y
= (x2 - 4x + 4) - (y2 - 4y + 4)
= (x - 2)2 - (y - 2)2
= (x - 2 - y + 2)(x - 2 + y - 2)
= (x - y)(x + y - 4)
b) (xy + 4)2 - 4(x + y)2
= (xy + 4)2 - [2(x + y)]2
= (xy + 4)2 - (2x + 2y)2
= (xy + 4 - 2x - 2y)(xy + 4 + 2x + 2y)
c) 25 - x2 + 2xy - y2
= 25 - (x2 - 2xy + y2)
= 52 - (x - y)2
=> (5 - x + y)(5 + x - y)
a) \(x^2-y^2-4x+4y=\left(x^2-y^2\right)-\left(4x-4y\right)=\left(x+y\right)\left(x-y\right)-4\left(x-y\right)\)
\(=\left(x-y\right)\left(x+y-4\right)\)
b) \(\left(xy+4\right)^2-4\left(x+y\right)^2=\left(xy+4\right)^2-\left(2x+2y\right)^2=\left(xy+4+2x+2y\right)\left(xy+4-2x-2y\right)\)
c) \(25-x^2+2xy-y^2=25-\left(x^2-2xy+y^2\right)=5^2-\left(x-y\right)^2=\left(5+x-y\right)\left(5-x+y\right)\)
x2 - y2 - 4x + 4y
= ( x2 - y2 ) - ( 4x - 4y )
= ( x - y )( x + y ) - 4( x - y )
= ( x - y )( x + y - 4 )
( xy + 4 )2 - 4( x + y )2
= ( xy + 4 )2 - 22( x + y )2
= ( xy + 4 )2 - [ 2( x + y ) ]2
= ( xy + 4 )2 - ( 2x + 2y )2
= [ ( xy + 4 ) - ( 2x + 2y ) ][ ( xy + 4 ) + ( 2x + 2y )
= ( xy - 2x - 2y + 4 )( xy + 2x + 2y + 4 )
25 - x2 + 2xy - y2
= 25 - ( x2 - 2xy + y2 )
= 52 - ( x - y )2
= ( 5 - x + y )( 5 + x - y )