Question

X^2 -kx-15=0 where -3 is one solution

Answer 1

You mean: What is k if -3 is one of the solutions or is the only solution. Poorly formatted but I'll answer it anyway.

We have

`x^2-kx-15=0`.

Then substitute x with -3 and solve for k

`</p><p>(-3)^2-k(-3)-15=0 \\</p><p>9+3k-15=0 \\</p><p>3k=6\Longrightarrow k=(6)/(3)=\boxed{2}</p><p>`

Hope this helps.