=25m^2-4-25m^2+40m-16-40m=-20
(5m-2)(5m+2) - (5m-4)² - 40m=
25m²-4-(25m²-40m+16)-40m=
25m²-4-25m²+40m-16-40m=
-20
=25m^2-4-25m^2+40m-16-40m=-20
(5m-2)(5m+2) - (5m-4)² - 40m=
25m²-4-(25m²-40m+16)-40m=
25m²-4-25m²+40m-16-40m=
-20