Polynomial PSAT Practice Test Question

p(x) = 3(x^2 + 10x + 5) - 5(x - k)

In the polynomial p(x) defined above, k is a constant. If p(x) is divisible by x, what is the value of k?

A) -3       B)-2      C)0      D)3

And please explain how you got the answer, like what method you went through to get the answer.