Question

caucule
1) (a + xy) ( a - xy) =
2) (-2a+b) (a-b) =

Answer 1

a)
(a + xy) . (a - xy) =
a² + axy - axy - x²y² =
a² - x²y²

b)
(-2a + b). (a - b) =
-2a² + ab +2ab - b² =
-2a² + 3ab - b²