Question

quick math help ?
Find the derivative of f(x) = -12x2 + 9x at x = 6.

-112.5
-135
-90
-108

Answer 1

\(\large\color{black}{ \displaystyle f(x) = -12x^2 + 9x }\)

apply the power rule to each term

Answer 2

f(x)=24x+9x ??

Answer 3

\(\large\color{black}{ \displaystyle f{\tiny~~}'(x) = -(\color{red}{2})12x^{\color{red}{2}-1} + (\color{red}{1})9x^{\color{red}{1}-1} }\)

\(\large\color{black}{ \displaystyle f{\tiny~~}'(x) = -24x + 9 }\)

Answer 4

\(\large\color{black}{ \displaystyle f{\tiny~~}'(\color{blue}{6}) =-24(\color{blue}{6})+9 }\)

Answer 5

(all you got to do, is to simplify this)

Answer 6

-135?