Studying for Calc placement test: Q: 8^x/2^x-1, A: 2^2x+1

[denuked03]

Hi,

Getting ready to go back to college and will be taking a precalculus test for placement. I was given a practice exam to study from that comes with the answers, but it doesn't really do a great job of explaining how to get the answers.

here is the problem:

8^x =
2^x-1

the answer is: 2^2x+1

I have no idea how to get that answer. Thank you in advance for your help!

[nona.m.nona]

What were the instructions for this expression?

When you reply, please provide a clarification of the exercise, using the formatting standards explained here. Thank you.

[denuked03]

What were the instructions for this expression?

When you reply, please provide a clarification of the exercise, using the formatting standards explained here. Thank you.

The instructions are "Find the value"

The purpose of the exercise is to gage my mathematical abilities.

The problem written a different way...

[8^x]/[2^(x-1)] = 2^(2x+1)

I am just wondering how they got there. I am looking for the steps from start to finish. It has been 10 years since I've done math like this. Thanks again for trying. I am new to this website and will try to help you help me if I can.

[nona.m.nona]

From the "answer" you have posted, the instructions should have been something along the lines of "simplify". To "find the value", they would have had to give you a numerical value for "x", and the answer would have been a numerical "value".

A good start for simplifying would be to convert 8 to a power of 2, and then use exponent rules to simplify the result.

An a related note, you might want to read this article on placement tests.