Question

If (x + 1) is a factor of (2x² + kx), then k = ?
(a) 4
(b) −3
(c) 2
(d) –2

Answer 1

(c) 2

$$\begin{gathered} \left(x+1\right)\text{is a factor of}2x^2+kx. \\ \mathrm{So},-1\mathrm{is}\mathrm{a}\mathrm{zero}\mathrm{of}2x^2+kx. \\ \mathrm{Thus},\mathrm{we}\mathrm{have}: \\ 2\times {\left(-1\right)}^2+k\times \left(-1\right)=0 \\ \Rightarrow 2-k=0 \\ \Rightarrow k=2 \end{gathered}$$