Question

Разложите на множители: 4х-х^2+у^2-4у

Answer 1

$4x-x^2+y^2-4y = (4x-4y) - (x^2-y^2) = \\ = 4(x-y) - (x-y)(x+y) = \\ = (x-y)(4-(x+y)) = (x-y)(4- x-y).$