SOLUTION: {{{system((1/2)^(x+y)=16, log(x-y,8)=-3)}}}. Calculate the values of x and y

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Question 173597: system%28%281%2F2%29%5E%28x%2By%29=16%2C+log%28x-y%2C8%29=-3%29. Calculate the values of x and y
Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!
system%28%281%2F2%29%5E%28x%2By%29=16%2C+log%28x-y%2C8%29=-3%29. Calculate the values of x and y

Let's simplify the equations.

Simplifying the first equation:

matrix%281%2C3%2C%281%2F2%29%5E%28x%2By%29%2C%22=%22%2C16%29

Write %281%2F2%29 as %282%5E%28-1%29%29
And write 16 as 2%5E4

matrix%281%2C3%2C%282%5E%28-1%29%29%5E%28x%2By%29%2C%22=%22%2C2%5E4%29

Remove the parentheses by multiplying the
inner exponent -1 by the outer
exponent x%2By, getting -x-y

matrix%281%2C3%2C2%5E%28-x-y%29%2C%22=%22%2C2%5E4%29

The base on each side is the same
positive number, which is not 1, so
we may equate the exponents:

matrix%281%2C3%2C+-x-y%2C+%22=%22%2C+4%29

Let's multiply every term by -1

matrix%281%2C3%2C+x%2By%2C+%22=%22%2C-4%29

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Now we simplify the second equation:

log%28x-y%2C8%29=-3

Use the rule of logs:  log%28B%2CC%29=A can be rewritten B%5EA=C

matrix%281%2C3%2C%28x-y%29%5E%28-3%29%2C+%22=%22%2C+8%29

Write 8 as 2%5E3

matrix%281%2C3%2C%28x-y%29%5E%28-3%29%2C+%22=%22%2C+2%5E3%29

Enclose both sides in parentheses and raise to the
1%2F3 power:



Multiply inner exponents by outer exponents:

matrix%281%2C3%2C%28x-y%29%5E%28-1%29%2C+%22=%22%2C+2%5E1%29 

Write the left side as 1%2F%28x-y%29 and right side as just 2 

matrix%281%2C3%2C1%2F%28x-y%29%2C+%22=%22%2C+2%29

Multiply both sides by %28x-y%29

matrix%281%2C3%2C1%2C+%22=%22%2C+2%28x-y%29%29

matrix%281%2C3%2C1%2C+%22=%22%2C+2x-2y%29

Put the right side on the left and vice-versa:

matrix%281%2C3%2C2x-2y%2C+%22=%22%2C+1%29

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So we now have this simpler system of equations:

system%28x%2By=-4%2C+2x-2y=1%29

I assume you know how to solve that system.
If you don't, post again asking how:

Answer:  matrix%281%2C3%2Cx=-7%2F4%2C+%22%2C%22%2C+y=-9%2F4%29

Edwin