( 5m+7n)x( 2n+ 4m)
( 12a+b)x(3a+5b)
( 2x-3y)x(2x+3y)
( 5m-2n)x(3n-5m)
(-a-b)x( 2a-3b)
( -7x-4y)x(-5x+7y)
(a2+b2)x(a2+b2)
( mn3-m2)x(m-1)
( 2x 2-y2)x( y2+ 2x3)
( xy2+3a2)x( 3xy+a3)