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Indices Question

Hi,

I'm struggling on this question, any advice would be appreciated (working included):

Solve y:

(9^y)/(27^2y+1) = 81

((3^2)^y)/((3^3)^2y+1) = 3^4

(3^2y)/(3^6y+3) = 3^4

2y/(6y+3) = 4

2y = 4(6y+3)
2y = 24y + 12
22y = 12
y = 12/22
y = 6/11

But I know the answer to be y= -7/4. Any help would be much appreciated, I've been at this problem for ages!
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Avatar for Naruke
Naruke
11
Original post by AndINeedHelp

2y/(6y+3) = 4


What did you do here?
Original post by AndINeedHelp
Hi,

I'm struggling on this question, any advice would be appreciated (working included):

Solve y:

(9^y)/(27^2y+1) = 81

((3^2)^y)/((3^3)^2y+1) = 3^4

(3^2y)/(3^6y+3) = 3^4

2y/(6y+3) = 4




Incorrect. Should be (2y)−(6y+3)=4(2y)-(6y+3)=4 as you subtract the indices when bases are identical.

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