X² + ax² - y - ay + cx² - cy = (x² + ax² + cx²) - (y + ay + cy) =
= x²(1 + a + c)- y(1 + a + c) = (1 + a + c)(x² - y)
x²y + x + xy² + y + 2xy + 2 = (x²y + xy² + 2xy) + (x + y + 2) =
= xy(x + y + 2) + (x + y + 2) = (x + y + 2)(xy + 1)
x² - 10x + 24 = (x - 4)(x - 6)
x² + 8x + 7 = ( x + 7)(x + 1)