Question

1/(2x^2-9x) use the chain rule. please help, I'm stressing out :(

Answer 1

what do u need to do evaluate the expression?

Answer 2

find the derivative using the chain rule.

Answer 3

you mean like find what f(x) and g(x) are?

Answer 4

ye

Answer 5

that'swhy i'm stucck, I'm guessing f(x) is 1/2 or -1/2 and g(x) is 2x^2-9x

Answer 6

haha. the concept is, derivative from the outside then going inside

Answer 7

so you're going to have, ln(2x^2 - 9x) x (4x-9)

Answer 8

how did you get that?

Answer 9

@Jeffrey_Calderon how did u get that please explain!

Answer 10

let u = 2x^2 -9x
then the dreivative of 1/u is ln(u) du

Answer 11

then your du = 4x-9
then substitute.got it?

Answer 12

i get uuuu

Answer 13

so the outside is 1/x which according to the properties is lnx, is that what you did?

Answer 14

yes!

Answer 15

ok thanks :) what do you mean by substitute?

Answer 16

substitute, replace,

Answer 17

i know but ehat is it that you would substitute into what?

Answer 18

2x^2 - 9x = u

so replace 2x^2 - 9x with u in the equation

derivative of 1/u

Answer 19

i'm sorry, I'm not understanding, could you maybe sow me what that would look like?

Answer 20

from your original equation. derivative of (1/(2x^2-9x)
since you replace the denominator by u,
it is going to be, derivative of 1/u

got it miss pretty?

Answer 21

i don't get what you mean by u, we didn't learn it that way

Answer 22

ok then give me your formula to rewrite my equation

Answer 23

just tell me what u stands for, and I'm pretty sure I'll get it

Answer 24

it's just a variable to simplify the equation, from the formula, the derivative of 1/x is ln(x) dx

or derivative of 1/u is ln(u)du

got it? i only used u because x is already in use

Answer 25

or derivative of 1/f(x) is equal to ln(f(x)) f'(x)

Answer 26

ok thank you

Answer 27

you got it?

Answer 28

no, but it's ok, i'll ask my teacher tomorrow :)

Answer 29

haha. sure. take note of the final answer though.

Answer 30

was that ln(2x^2 - 9x) x (4x-9)?

Answer 31

yea, that's times, not x. ok?
\[(4x-9) \ln (2x ^{2}-9x)\]

Answer 32

yeah, I get you, thanks again.