Question

if 3 is a zero of the polynomial xsqaure +2x -a.find a​

Answer 1

x²+2x -a

$\to (3)²+2(3)-a \\ \\ \to 9+6-a \\ \\ \to 15-a =0 \\ \\ \to a =-15$

Answer 2

Given,

3 is the zero of p(x)

where p(x) = x² + 2x - a

$that \: is \: \: \: {x}^{2} + 2x - a = 0$

$p(3) = {(3)}^{2} + 2(3) - a = 0 \\ 9 + 6 - a = 0 \\ 15 - a = 0 \\ 15 = a \\ a = 15$