If 3 is a zero of the polynomial
Question:

If 3 is a zero of the polynomial $2 x^{2}+x+k$, find the value of $k$.

Solution:

Given: x = 3 is one zero of the polynomial 2x2 + x + k
Therefore, It will satisfy the above polynomial.
Now, we have

$2(3)^{2}+3+k=0$

$\Rightarrow 21+k=0$

$\Rightarrow k=-21$