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## Comment on

Power of 5## ammmmmmazing videos!! loved

## Thanks!

Thanks!

## Hi Brent!

I stumbled a little bit in the beginning but got to the answer eventually. My question is, in an expression like the one above, would it be fair to equate 5^(3x+1) to 5^1, even with the 4 present?(Assuming that we split 20 into 5 times 4) eg:5^(3x+1) = 5^1 *4^1

## Yes, that's correct.

Yes, that's correct.

If 5^(3x+1) = 20, then we can also say that 5^(3x+1) = (5^1)(4^1)

Cheers,

Brent

## hi brent,

so the part where multiplied powers of both sides by 1/3. that was to eliminate 3 from 3x correct?

## That's correct.

That's correct.

Our goal is to determine the value of 5^(-x), so I needed a way to eliminate the 3 from 3x.

Cheers,

Brent

## Hi Brent,

In this question:

What is the cube root of w?

(1) The 5th root of w is 64.

(2) The 15th root of w is 4.

Do we really have to solve equation 1 and 2 to get the answer? Or just by looking at the equations, we know that since the 5th and 15th root of w is given, it should be possible to find the cube root of w and both equations 1 & 2 should suffice?

I want to confirm if we have to solve this to prove it or if we can just see the statements and directly choose answer D.

## Your reasoning is perfect.

Your reasoning is perfect.

Since we COULD determine the actual value of w from each statement, we COULD calculate the cube root of w.

In other words, we COULD answer the target question with certainty.

Here's my full solution: https://gmatclub.com/forum/what-is-the-cube-root-of-w-136884.html#p2626640