Question 887437
Use the remainder theorem: x - k is a factor of the polynomial P(x) if P(k) = 0.  Otherwise, P(k) becomes the remainder when P(x) is divide by x - k.

Proceeding thus, P(1) = 2 + 3 - 12 - 7 +6 = -8

Hence, x - 1 is NOT a factor of {{{P(x)=2x^4 + 3x^3 - 12x^2 - 7x +6}}}.