( 7x + 7a) - 5a(x - a) = 7(x + a) - 5a(x - a) проверьте знаки в условии
(5y^2 + 5) + (y + y^3) = 5(y^2 + 1) + y( 1 + y^2) = (y^2 + 1)(5 + y)
(y^3 - 2y^2) - 2(2 - y) = y^2(y - 2) + 2(y - 2) = (y - 2)(y^2 + 2)
(7c^2 + 7) - c(1 + c^2) = 7(c^2 + 1) - c( c^2 + 1) = ( c^2 + 1)(7 - c)