Functions f and g are differentiable at x=2 and satisfy the following:
f(2)=3,f′(2)=−1,g(2)=−4,g′(2)=5.
Let P(x)=f(x)g(x).
(a) Determine the value of P′(2).
(b) Explain, using complete sentences, why knowledge of both f′(2) and g′(2) is essential for finding P′(2). Your explanation should reference the quantities calculated in part (a).