I keep getting it wrong

Question

8^x-1 = 4 

 

how do i approach this

Answer 1

Student,

 

It is not clear whether you mean

 

8^{x - 1} =  4

 

or

 

8^x -  1 = 4.

 

I will work both.

 

(A)

 

8^{x - 1} = 4

 

(x - 1)log₂8 = log₂4

 

(x - 1)(3) = 2

 

Now solve for x and finish from here.

 

(B)

 

8^x - 1 = 4

 

8^x = 5

 

x log8 = log5

 

x = log5 / log8

 

True for any base.