Question

If one zero of the quadratic polynomial x² + 3x + k is 2 , then the value of k is

(a) 10 (b)$-$10 (c) 5 (d)$-$5

Answer 1

Let the given polynomial be f(x) = x² + 3x + k.
Since 2 is one of the zero of the given plynomial, so (x − 2) will be a factor of the given polynomial.
Now, f(2) = 0
$$\begin{gathered} \Rightarrow 2^2+3\times 2+k=0 \\ \Rightarrow 4+6+k=0 \\ \Rightarrow k=-10 \end{gathered}$$
Hence, the correct answer is option B.