The factor theorem states that a polynomial f(x) has a factor (x−k) if and only if f(k)=0. If x−1 is a factor, then x=1 is a root.
To verify the root, substitute x=1 in f(x)=0.
f(x)=2x3+11x2−7x−6
f(1)=2(1)3+11(1)2−7(1)−6
0=2+11−7−6
0=0
Therefore, the given factor (x−1) is a factor of 2x3+11x2−7x−6