AS Maths question

[AngloScot]

I am stuck on the following question and the answer/method is not in the book please help!!

Given that 3^x = 9^(y-1), show that x=2y-2

NB Where I have used ^ i mean 'to the power of'.

[PFD]

here's a hint: 9=3^2

[andyharrison]

2y-2 = 2(y-1)

do you need any more hints?

[mbee]

If the above two haven't helped you enough, here's step by step explanation:

3^x = 9^(y-1)

3^x = (3^2)^(y-1)  (as 9= 3^2)

3^x = 3^(2y-2) (as powers can be multiplied where there are brackets, that's not a very clear explanation but I'm sure you'll understand)

 

Therefore:

x= 2y-2

P.S. Don't worry, I'm doing AS maths too and it's pretty difficult.

[AngloScot]

Cheers mbee, the method was what i was looking for.