4) (x+y)^2-(x-y)^2 5) (4p-q)^2-(2p+3q)^2 pls
(х+у+х-у)(х+у-х+у)=2х*2у=4ху (4p-q+2p+3q)(4p-q-2p-3q)=(6p+2q)(2p-4q)=4(3p+q)(p-2q)