SOLUTION: 8^(3x-2)=64

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Question 250492: 8^(3x-2)=64
Answer by jsmallt9(3758) About Me  (Show Source):
You can put this solution on YOUR website!
8%5E%283x-2%29+=+64
The simplest solution is found by recognizing that 64 is a power of 8. So we can rewrite the equation as:
8%5E%283x-2%29+=+8%5E2
Since both sides are results of raising 8 to a power, the exponents must be equal:
3x-2+=+2
Solving this:
3x+=+4
x+=+4%2F3

If we don't notice that 64+=+8%5E2 we can solve this using logarithms. We can use any base of logarithm. But we should pick a base our calculator can find. So I will use base 10:
log%28%288%5E%283x-2%29%29%29+=+log%28%2864%29%29
Now we can use a property of logarithms, log%28a%2C+%28p%5Eq%29%29+=+q%2Alog%28a%2C+%28p%29%29, to move the exponent of the argument out in front. (This is the reason we use logarithms on problems like this: to get the variable out of the exponent.)
%283x-2%29log%28%288%29%29+=+log%28%2864%29%29
Now we solve for x. Divide both sides by log%28%288%29%29:
%283x-2%29+=+log%28%2864%29%29%2Flog%28%288%29%29
Add 2 to each side:
3x+=+2+%2B+log%28%2864%29%29%2Flog%28%288%29%29
Multiply both sides by 1/3:
x+=+2%2F3+%2B+log%28%2864%29%29%2F3log%28%288%29%29
If we enter the expression on the right into our calculator we end up with
x = 1.333333...
which is 4/3 in decimal form.