To find the slope you divide the difference of the y-coordinates of 2 points on a line by the difference of the x-coordinates of those same 2 points. Its slope is 0. The difference quotient gives the precise slope of the tangent line by sliding the second point closer and closer to 7 9 until its distance from 7 9 is infinitely small.
Because the slopes of perpendicular lines neither of which is vertical are negative reciprocals of one another the slope of the normal line to the graph of f x is 1 f x.
If you carefully placed a ball on the floor it would not roll. The slope of a horizontal line y b y b is 0. Find the equation of the normal line to the curve y x 3 at the point 2 8. Now equation of a normal line at point 1 -3 and with slope -1.