# Thread: derivatives with a graph

1. ## derivatives with a graph

Consider the function and tangent line shown below. Suppose f(6) = 72, f '(6) = 1.5, a = 6, b = 6.2, and c = 5.9.

im looking for the coordinates of point B and C...i now that the X value for B is 6.2 and C is 5.9...i just dont know where to start to get the y values...please help...

2. Originally Posted by mer1988
Consider the function and tangent line shown below. Suppose f(6) = 72, f '(6) = 1.5, a = 6, b = 6.2, and c = 5.9.

im looking for the coordinates of point B and C...i now that the X value for B is 6.2 and C is 5.9...i just dont know where to start to get the y values...please help...
the points are all on a straight line.

use the point slope form for the point A(6,72), thus we have:

$y - 72 = 1.5(x - 6)$

solve that for y, that will give you the equation of the line. then you just plug in the x-values for B and C to find their y-values