Question

Find dy/du, du/dx, and dy/dx when y and u are defined as follows.
y = √u u = 7x - 6x2

Answer 1

must derive y= sqrt. of u
and u=7x-6x2

or is that 6x^2?

Answer 2

@DarlaD so what did you get when you derive y and u?

Answer 3

uhmm.. pls. reply? :D can you derive y an u?

Answer 4

its 6x^2

Answer 5

okay so what did u get for dy/du and the rest? :)

Answer 6

I don't know

Answer 7

now that we already get dy and du... what is dy/du? :)

Answer 8

1/2u^(-1/2)/7-12x but how do you reduce that

Answer 9

sorry my bad wait

Answer 10

i mean when you derive y it is dy/du

so
y= sqrt. of u
\[\frac{ dy }{ du }= \frac{ 1 }{ 2 }u ^{\frac{ -1 }{ 2 }}\]

u = 7x-6x^2
\[\frac{ du }{ dx }= 7 - 12x\]

now using the chain rule:

dy/dx = dy/du * du/dx

\[\frac{ dy }{ dx }= (\frac{ 1 }{ 2 }u ^{\frac{ -1 }{ 2 }}) * (7 - 12x)\]

Answer 11

since u = 7x - 6x^2

substitute that to
\[\frac{ 1 }{ 2 }u ^{\frac{ -1 }{ 2 }}\]
it'll be
\[\frac{ 1 }{ 2 }(7x-6x^2)^{\frac{ -1 }{ 2 }}\]

Answer 12

Is there a different form Is should put it in? the answer still isn't right

Answer 13

\[\frac{ dy }{ dx }= (\frac{ 1 }{ 2 }(7x-6x^2)^{\frac{ -1 }{ 2 }})*(7-12x)\]

Answer 14

what do you mean? :) we're not yet getting th efinal answer :)

Answer 15

ohh ok

Answer 16

:)

Answer 17

So is that not the final answer?

Answer 18

not yet... wait a second...