Need help in doing math...

[TimBluesWin]

Hello everyone...

I'm now doing O/N 2012 p31, and I seem to stuck on no 2, about solving the equation of 5^(x-1)=5^(x)-5

I know I can look on marking scheme directly, but I don't want to do that.... So can anyone help me to find the solution? Thanks!

 

[Nibz]

Since the bases on both sides (being 5 here) are equal, you can simply equate the powers.

x - 1 = -5x
x = 1/6

 

[TimBluesWin]

Since the bases on both sides (being 5 here) are equal, you can simply equate the powers.

x - 1 = -5x
x = 1/6

Sorry if I keep asking, but why 5^x - 5 can become -5x when we equate the powers?