Math Help - Trouble with Tangents

1. Trouble with Tangents

I can't figure out how to solve this problem:
finf k such that the line is tangent to the graph of the function.
x^2-kx y=4x=9
Can someone help me understand this problem?

2. Originally Posted by alecbyrd
I can't figure out how to solve this problem:
finf k such that the line is tangent to the graph of the function.
x^2-kx y=4x=9
Can someone help me understand this problem?
Did you mean that we were to find k, such that $y = 4x + 9$ is a tangent to the curve $y = x^2 + kx$?

If so, remember that the derivative of a function gives the equation of the tangent of that function.

If you differentiate $y = x^2 + kx$, you get $dy/dx = 2x + k$. What you must do is compare this to $y = 4x + 9$ in order to find k.

3. Originally Posted by alecbyrd
x^2-kx y=4x=9
Does this equation make sense?