Question

y/9=4-9x....y/9=4x-9/x ... now im stuck. I need to solve for y.

Answer 1

I tried Mulitplying both sides by 1/9, but I dont think that would work

Answer 2

multiply both sides with 9

Answer 3

and then solve further

Answer 4

I got 36x-81/9x

Answer 5

wait i will solve it send yu a pic

Answer 6

y/9=4-9x
y = 9*(4-9x)
y = 36 - 81x

substitute this to ..y/9=4x-9/x

y/9=4x-9/x
y = 9*(4x-9/x)
y = 36x - 81/x
y = (36x^2 - 81)/x
xy = 36x^2 - 81
x(36 - 81x) = 36x^2 - 81
36x - 81x^2 = 36x^2 - 81
36x = 36x^2 +81x^2 - 81
36x = 117x^2 - 81
0 = 117x^2 -36x -81

Answer 7

then

Answer 8

@sheetalvee in the 2nd equation is the whole thing on top of x or only 9?

Answer 9

just to explain that
y is already multiply by 1/9 that's why its y/9
so that's why you multiplying both side 9

Answer 10

wait, okay I need to solve for y right, then after I need to differentiate to get y1

Answer 11

117x^2 -36x -81 = 0
9(13x^2 -4x -9) = 0

Answer 12

117(x -(2/13))^2 - (1089/13) = 0

Answer 13

\[117(x - \frac{ 2 }{ 13 })^2 - \frac{ 1089 }{ 13 } = 0\]

Answer 14

oh pellet, Guys Im sorry, It wa 9/y = 4x-9 / x

Answer 15

Thats why I said mulitply both sides by 1/9

Answer 16

So

\[x = - {\frac{ 9 }{ 13 }}\]
\[x = 1\]

Answer 17

Now Im just confusing myself. Ill send you the actual question

Answer 18

hmmm :(

Answer 19

\Part b

Answer 20

you can go ahead and solve it for \(y\) in maybe 3 steps

Answer 21

I got up to this step: 9/y=4x-9/x

Answer 22

\[\frac{9}{x}+\frac{9}{y}=4\\
\frac{9}{y}=4-\frac{9}{x}=\frac{4x-9}{x}\]

Answer 23

then flip it and get
\[\frac{y}{9}=\frac{x}{4x-9}\]

Answer 24

multiply by 9 and get
\[y=\frac{9x}{4x-9}\]

Answer 25

find the derivative via the annoying but useful quotient rule

Answer 26

9/y = 4 - (9/x)
y = 9/(4 - (9/x))
y = 9 * (x/(4x-9)) = 9x/(4x -9)

Answer 27

how is that webassign anyways?

Answer 28

wasnt i suppose to multiply 4x-9 by 9 aswell ?

Answer 29

no

Answer 30

why not

Answer 31

\[\frac{x}{9}=\frac{4}{5}\\
x=\frac{9\times 4}{5}\]

Answer 32

you are not building up a fraction by multiplying top and bottom by some number
you are multiplying a fraction by a number

Answer 33

multiply means multiply in the numerator, not multiply top and bottom

Answer 34

Ohhhhhhhhhh yesss. Thank you !

Answer 35

and what was the question about webassign

Answer 36

\[\frac{ d }{ dx } \left( \frac{ 9x }{ 4x-9 } \right) = -{\left( \frac{ 81 }{ (9-4x)^2} \right)}\]

Answer 37

the question was, how is that webassign? easy? hard? annoying??

Answer 38

Um it's okay. The questions are similar to our textbook so it's not bad as long as we finish the textbook questions. But Im doing it together which I realize now I shouldn't. Overall it should be easy if I had done the textbook questions first

Answer 39

its simple all you need to do is bring both the equations in standard form that is you should isolate y or x in both the equations then simply substitute the vale of any ne equation into the other and solve for y-IF U KNOW WHAT I MEAN

Answer 40

its a trick question i got it

Answer 41

hold on for a sec i will upload a pic

Answer 42

@sheetalvee okay i got yuo

Answer 43

@sheetalvee here's what i think you see both equation =y/9 so you can set both part on right side equal to each other and solve for x and then substitute your value for x in any one of the original equations to get y

Answer 44

@sheetalvee let me know what you think

Answer 45

Yep I got it ! :)