Question

Given f(x) = 3x³ + x + k, and x + 1 is a factor of f(x), then what is the value of
k?

Answer 1

Answer: k=-2

Explanation:

`\displaystyle\\3 x^2+x+k=\\\\3x^2+3x-2x+k=\\\\3x(x+1)-2(x-(k)/(2)) \\\\Hence,\\\\x-(k)/(2) =x+1\\\\-(k)/(2) =1\\`

Multiply both parts of the equation by -2:

`\displaystyle\\-(k)/(2)(-2) =1(-2)\\\\k=-2`