Calculus
posted by Si .
Find the average or mean slope of 2x^3  6x^2  90x +3 on the interval [6,10]?
By the Mean Value Theorem, we know there exists at least one c in the open interval ( 6 , 10 ) such that f'( c) is equal to this mean slope.
::>> I already found the mean slope of the function which is 38. Now I'm trying to find "c". I can't get c.

6x^2  12 x 90 = 38 ??? assuming your 38 is correct
6 x^2  12 x  128 = 0
3x^2  6 x  64 = 0
x =5.73