Trả lời :
x2 - y2 - 4x - 4y
= (x2 - y2) - (4x + 4y)
= (x + y) . (x - y) - 4 . (x + y)
= (x + y) . (x - y - 4)
Ta có : x2 - y2 - 4x - 4y
= x2 - y2 - 4(x + y)
= (x - y)(x + y) - 4(x + y)
= (x + y)(x - y - 4)
x2 - y2 - 4x - 4y
= ( x2 - y2 ) - ( 4x + 4y )
= ( x + y )( x - y ) - 4( x + y )
= ( x + y )( x - y - 4 )
\(x^2-y^2-4x-4y\)
\(=(x-y)(x+y)-4(x+y)\)
\(=(x+y)(x-y-4)\)