In order to find any of the info we need we have to find the first derivative of the equation. If 
, then 
. We are told to find the slope at point (1, 7). Using that x value in our derivative will give us the slope of the line at that point. y' = -(1)^2+8. So y' = 7. That's the slope of the line. Now we will use that slope along with the x and y coordinate in the slope-intercept form of a line to solve for b. 7 = 7(1) + b so b = 0. Our equation then is y = 7x. If you graph these in the same window on your calculator, you can see how perfectly that align at the given point. It's really quite perfect.