SOLUTION: how do you solve -27^-2/3

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Question 1205780: how do you solve -27^-2/3

Found 2 solutions by Edwin McCravy, mccravyedwin:
Answer by Edwin McCravy(20059) About Me  (Show Source):
You can put this solution on YOUR website!
matrix%282%2C1%2C%22%22%2C-27%5E%28-2%2F3%29%29

First of all the negative sign is not the sign of 27, for it is
the sign of the entire expression.  The above is equivalent to
matrix%282%2C1%2C%22%22%2C-%2827%5E%28-2%2F3%29%29%29

The exponent is negative which means that it is the reciprocal
of the expression with an exponent with the positive sign.

matrix%282%2C1%2C%22%22%2C-%281%5E%22%22%2F27%5E%28%222%2F3%22%29%29%29

Now a fractional power with a 1 numerator is the root of the 
base with the same index.  So let's first write the fractional exponent 2/3
as (1/3)(2)

matrix%282%2C1%2C%22%22%2C-%281%5E%22%22%2F27%5E%28%221%2F3%22%2A2%29%29%29 

Then we use the law of multiplied exponents as

matrix%282%2C1%2C%22%22%2C-%281%5E%22%22%2F%2827%5E%28%221%2F3%22%29%29%5E2%29%29%29

Go back to the rule that a fractional power with a 1 numerator is the 
root of the base with the same index as the denominator of the 
fractional exponent.

matrix%282%2C1%2C%22%22%2C-%281%5E%22%22%2F%28%28root%283%2C27%29%29%5E2%29%29%29

The cube root of 27 is 3, so we have

matrix%282%2C1%2C%22%22%2C-%281%5E%22%22%2F3%5E2%29%29%29

And since 3 squared is 9, we have

-1%2F9

Edwin




Answer by mccravyedwin(407) About Me  (Show Source):
You can put this solution on YOUR website!
matrix%282%2C1%2C%22%22%2C-27%5E%28-2%2F3%29%29

You can also do it this way, skipping the "root" part.

matrix%282%2C1%2C%22%22%2C-27%5E%28-2%2F3%29%29
matrix%282%2C1%2C%22%22%2C-%283%5E3%29%5E%28-2%2F3%29%29
Multiply exponents:
matrix%282%2C1%2C%22%22%2C-%283%29%5E%283%2Aexpr%28-2%2F3%29%29%29
matrix%282%2C1%2C%22%22%2C-%283%29%5E%28cross%283%29%2Aexpr%28-2%2Fcross%283%29%29%29%29

matrix%282%2C1%2C%22%22%2C-%283%29%5E%28-2%29%29%29

matrix%282%2C1%2C%22%22%2C-%281%5E%22%22%2F3%5E2%29%29

matrix%282%2C1%2C%22%22%2C-1%2F9%29

Edwin