(x-6)(x+3)
3x2 - 15x + 42 = 3*(x2 - 5x + 14) which cannot be factorised further.
x2 - 36 = x2 - 62 = (x + 6)(x - 6)
x2-3x-28
7(3x+7)
(x-9)(x+1)
x2 - 41 cannot be factorised.
(x + 7)(x - 9)
x2-9x+18 = (x-3)(x-6) when factorised
x2 + 4x + 3 = (x + 1)(x + 3)
x2-2x-24 when factorised = (x+4)(x-6)
x2-6x+9 = (x-3)(x-3) when factorised.