2 questions, I need the formula, but if you can also give me the full answers for both, I'd be very thankful



This post was edited by penoyman on Nov 17 2013 05:45pm

1) 5^(x-1) = 25
(x-1)*log(5) = log(25) = 2*log(5)
x-1 = 2
x = 3

2)
2^(x+3) = 8*2^x
your equation is : 8*2^x + 2^x = 288
i.e. 9*2^x = 288, 2^x = 32, x = 5

while correct, the first one can be solved easier (and similar to the second one)
with 25=5^2 it is easy to see that x=3

or yet another way: 5^(x-1)=5^x/5 so the equation can be changed to 5^x=125

how did you get the 8 in the second question?

2^(x+3)=2^x*2^3 and 2^3=8

ok ty, it makes sense now, but I might reply back again though

Good thing about your equations here, they're simple enough that with a calculator, you can just use educated guesses and plug them in to check.