Hi guys, hope you are well. I want to understand why can I not eliminate x(common-term) from both sides? I did that and it gives me x^2-1^2 on left side and x^2 right. This led me to choose B as the option which is wrong.

Qty : A = x^3-x

Qty :B = x^3

Eliminate the common term x^3 and you’re left with

Qty : A = -x

Qty :B = 0

Now Qty A can be +ve or -ve depending upon the value you choose for x.

Hence, the answer is D

Hi @HoldMyBeer,

I do understand the approach you went with. I was wondering as to why i cannot eliminate x in the first step leaving (x-1)(x+1) on one side and (x)(x) on the other?

-Thanks

QC questions are inequalities, so what if x is a negative number?

As a rule of thumb, just never cancel out values in QC questions unless you’re sure that the numbers are positive!

Another easy way to do this would be to consider x=0 and x=2

For x=0, both answers will be 0(That is, they’ll be equal)

For x=2, none of the answers would be 0(That is, they won’t be equal)

Hence, correct answer would be D

@aka.das1996

I did the same thing on my first attempt, not considering it was inappropriate here.

This is exactly what I needed to see. I understand the FOIL method but its been years since I’ve run into math problems. Sometimes you just gotta brute force it to double check.