flynno37 wrote:

Hello,

I have been having difficulties with this question.

I originally got the question wrong so looked at the answer for help. It is on page 52 of GMAT review (red) book.

I'm trying to understand how the factoring works particularly the step from squaring both sides to the last line. I understand that I must use FOIL however I cannot work out how this is to be applied on the right-hand side.

If I may say, for a so-called "answer explanations" section this is the part which should be explained. The rest of the answer explanation has not given me a problem eventhough they are explained. So I am not so concerned about getting the answer right (creating 4x₂ on one side) as to understanding how we get from one step to another.

So basically can anyone help me to explain how (√2x+1)₂ becomes 2x + √2x+1 ?

Second degree equations

Work with the equation to create 4x₂ on one side.

√(〖3-2x〗^ ) = √2x+1

(√(〖3-2x〗^ ))₂ = (√2x+1)₂ Square both sides

3-2x = 2x + √2x+1

It may be that there is a piece of knowledge I am missing or I am applying FOIL wrong.

Any help would be appreciated!

Thank you,

This is where you have made your mistake.

First, Outside, Inside, Last

(√2x+1)*(√2x+1) = 2x + √2x + √2x + 1 = 2x+2√2x+1

Looks like you simply forgot to perform the operation on 1*√2x twice.

Hope this helped!