I'm struggling with the following. I have a question such as:

Find an equation for the line tangent to $\displaystyle y=3-5x^2$ at (5,-122)

I know how to calculate the slope which is:

$\displaystyle -50=(y-(-122))/(x-(5))$

And the above in slope intercept form is:

$\displaystyle -50x+128$

How was the slope intercept form calculated? I can't seem to figure this out.