xy + 3y + xz + 3z = y(x+3) + z(x+3) = (x+3)(y+z)
25 - c^2 = (5 + c)(5 - c)
ab^2 - 2abc + ac^2 = ab(b - 2c) + ac(b) = ab(b - 2c + a)
xy + 3y + xz + 3z = y(x+3) + z(x+3) = (x+3)(y+z)
25 - c^2 = (5 + c)(5 - c)
ab^2 - 2abc + ac^2 = ab(b - 2c) + ac(b) = ab(b - 2c + a)