Question

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

Answer 1

differentiate it using this
\[\frac{ d }{ dx }(cx^n) = cnx ^{n - 1}\]

Answer 2

i thought the formula was \[f(x + h) - f(x) / h\]

Answer 3

Thats for the limit isn't it?\[\lim_{h \rightarrow 0}\frac{ f(x + h) - f(x) }{ h }\]

Answer 4

oh yeah. so i use the other formula for the derivative?

Answer 5

Use the previous formula

Answer 6

im still confused, im not sure where to plug the numbers into

Answer 7

\[f(x) = -12x^2 + 9x\]\[f'(x) = -12(2)x + 9\]\[f'(x) = -24x + 9\]Now substitute x = 6 into the derivative.

Answer 8

153

Answer 9

???

Answer 10

24(6) + 9 ?

Answer 11

it's -24....

Answer 12

-135