Question

Given f(x) = x3 + kx + 16, and x + 2 is a factor of f(x), then what is the value
of k?

Answer 1

Explanation:

`f(x) = { x}^(3) + kx + 16 \\ \\ if \: x + 2\: is \: a \: factor \: of \: f(x) \\ f( - 2) = 0 .....(1)\\ f( - 2) = { (- 2)}^(3) + ( - 2)k + 16 \\ f( - 2)= - 8 - 2k + 16 .......(2)\\ \\ (1) = (2) \\ - 8 - 2k + 16 = 0 \\ - 2k = - 8 \\ k= 4`