Question

Calculate dy/dx
You need not expand your answer.

y=3x^2-9x+13/2x+4

Answer 1

dy/dx=

Answer 2

i got 3x^2+8x=26 which is clearly wrong

Answer 3

over 2(x+2)^2

Answer 4

yeah

Answer 5

gimmie a sec

Answer 6

kk thanks for helping

Answer 7

gah I hate quotient rule

Answer 8

the answer is 3x^2-9x+13/(2x+4)^2

Answer 9

now I will put my work on here

Answer 10

Do you know the quotient rule?

\[(u\div v)^'=(vu^'-uv')\div v^2\]

Answer 11

i got that too agentzero and it was wrong :/

Answer 12

actually 3x^2+12x-31/2(2x+4)^2

Answer 13

\[u = 3x{^2}-9x+13\]\[v = 2x+4\]
\[u' = 6x - 9\]\[v' = 2\]
\[y' = [((2x+4)\times(6x-9)) - ((3x{^2} - 9x + 13)\times 2)]\div (2x+4){^2}\]

Answer 14

thats what wolfram says.
This isnt hard I dont know why im getting it wrong

Answer 15

think i gotta go to a tutor for this one lol. thanks for the help

Answer 16

(2x+4)(6x-9)-(2)(3x^2-9x+13)
(12x^2+6x-36)-(6x^2-18x+26)
6x^2+24x-62/(2x+4)^2

6x^2+24x-62/4x^2+16x+16 factor a 2 out

3x^2+12x-31/2x^2+8x+8
=
3x^2+12x-31/2(x+4)^2

Answer 17

if thats not right then i dont know what is lol

Answer 18

I got the same answer twice

Answer 19

I just gave it to you...
\[y' = [((2x+4)\times(6x-9)) - ((3x{^2} - 9x + 13)\times 2)]\div (2x+4){^2}\]
\[(2x+4)(6x-9) - 2(3x^2 - 9x + 13) \over (2x+4)^2\]
\[(12x^2 - 18x + 24x - 36) - (6x^2 - 18x + 26) \over (2x+4)^2\]
\[(12x^2 + 6x - 36) - (6x^2 - 18x + 26) \over (2x+4)^2\]
\[6x^2 + 24x - 62 \over (2x+4)^2\]
You can simplify it further but it's not necessary:
\[3x^2 + 12x - 31 \over 2(2x+4)^2\]

Answer 20

There's three basic rules you MUST know for differentiation:

The product rule: \[(uv)' = u'v + uv'\]
The quotient rule: \[(u\div v)' = {(vu' - uv')\over v{^2}}\]
The chain rule: \[f[g(x)]^'=f^' [g(x)]\times g(x)\]

Answer 21

@AgentZero: for problems you are given (i.e. not "real world" problems) you generally do not need to mess with the denominator. Once you have (vu' - uv')/v^2 you can generally just simplify the numerator and stop there.

Answer 22

sure but Im assuming this is computer homework and it would probably want denominator too

Answer 23

3x^2+12x−31/2(2x+4)2 yeah its for webassign. I the answer you both got on first try but it still doesnt accept it

Answer 24

i got the same answer you both got is what im saying* but webassign didnt accept it..

Answer 25

I have a lot of experience with webassign and I can say it is terrible =)

Answer 26

to fewscrewsmissing
your answer is good except the last denominator
it should be 2(x+2)^2

Answer 27

he did in his last answer

Answer 28

you probably didn't pay attention inside of () is x+2

Answer 29

Yes you're right MarinaDL, thanks for pointing that out.

I would normally stop prior to this step anyway. Apparently this particular assignment is requiring very specific input.... richstyle I'd just suggest playing around with it until it accepts it?