( 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)
(5m+7n)*(2n+4m)= 10mn+20m+14n+28mn