`f(x) = k - x^2, y = -6x + 1` Find k such that the line is tangent to the graph of the function.
The tangent line will touch a point on the function f(x).
Set both equations equal to each other.
With two unknown variables, we will need another relationship of x and k.
Take the derivative of f(x) and set the derivative function equal to the slope of the tangent line equation. The slope of the tangent line is negative 6.
`-6 = -2x`
We can find k by substituting back the value of x into the first equation.
`k-9 = -18+1`