x3 + x2 + 4x + 4 = (x2 + 4)(x + 1)
x + 4
x2(x3 + 1) is the best you can do there.
You can't factor it
That does not factor neatly.
Not factorable
1
x2+10x-336
x2 + 5x - 120 can not be factored.
x2 - 13 + 30 = x2 + 17, which has no real factors.
x2 + 26x + 48 = (x + 24)(x + 2)
x2 + 7x + 6 = (x + 6) (x + 1)