Finding points on a tangent line

[Vandella]

Homework Statement

Find the point(s) on the graph of the function at which the tangent line has the indicated slope. (If an answer does not exist, enter DNE.)

g(x) = (1/3)x^3 - (1/2)x^2 - 4x +8

mtan=-4

Homework Equations

3. The Attempt at a Solution

firstly i derived g(x) to give x^2-x-4
as tangent line = -4 substituted into equation to give x^2-x-4=-4
manipulated to get x^2-x=0
that gave me x=0 or x=-1
used those values in original function to find y values
points i obtained were (0,8) and (-1,67/6)

when i enter these with lowest x value first it says i am wrong please help

 

[Stimpon]

Since this is just a silly brainfart mistake I'm going to give you the answer, x=-1 is not a solution, you made a silly mistake when you solved the quadratic.

 

[Vandella]

ahhh i can't believe i missed that

thanks