3x squared minus 25x minus 28
-20
x2 - 9x + 20 = (x - 4)( x - 5)
(a + 3)(a - 3)
(5x - 2y)(5x + 2y)
(2a - b)(2a + b)
(z - 8x)(z + 8x)
Sixteen.
Negative twenty nine minus negative twenty one is negative eight.
(x + 1)(x - 8)
Without that other number, all you've got is zero.
2x squared - 5x - 3 = (2x +1)(x -3)