What is k if f(x)=x^2-kx-3 and f(2)=9 ?

Given f(2) = 9 , we have to find k in the function f(x) = x^2 -
kx - 3.

Now f(x) = x^2 - kx - 3, for x
=2

=> f(2) = 2^2 - k*2 - 3 =
9

=> 4 - 2k - 3 = 9

=> 2k
= 4 - 3 - 9

=> 2k = -8

=>
k = -8/2 = -4

Therefore the value of k is -4 and the
function f(x) is x^2 + 4x - 3.