x4 + 2x3 - 9x2 + 18x = x(x3 + 2x2 - 9x + 18) which I do not think can be factorised further.
No.
2x to the fourth power minus 162 equals -146
It is: (x-y)4
-16,128
x^2(x - 4)(x + 4)
3x^3(x - 4)
(3x^2 - 4y^2)(3x^2 + 4y^2)
(x2 + 1)(x2 - 2)
(x2 - 2)(x2 + 2)
x(x - 1)
(2x - 3)(3x + 2)
a3x2 - 216x2 factors to x2(a - 6)(a2 + 6a + 36)