Разложите на множители; 1) a^2-b^2-a+b 2) a^3+a^2b-ab^2-b 3) xs-ys-x^2+2xy -y^2

1) a² - b² - a + b = ( a² - b²) - ( a -b) = ( a - b)( a + b) - ( a - b) = ( a -b)(a + b - 1)
3) xs - ys - x² + 2xy - y² = (xs - ys) - ( x² - 2xy + y²) = s( x - y) - ( x - y)² =
= s( x - y) - ( x - y)(x - y)= ( x - y)( s - x + y)
2) проверьте условие