# Lesson: Combining Factoring Techniques

## Comment on Combining Factoring Techniques

### Hi. I noticed that there is a

Hi. I noticed that there is a lot of practice with difference of squares. Do you know of any sources that can provide practice with the other two special products?

Thank you!!

### f a, b, and c are constants,

f a, b, and c are constants, a > b > c, and x^3 - x = (x - a)(x - b)(x - c) for all numbers x, what is the value of b ?

(A) - 3
(B) -1
(C) 0
(D) 1
(E) 3

Hi Brent,

Thanks a lot
Fatima-Zahra

### Nice question! I've now added

Nice question! I've now added it to the Reinforcement Activities.

Here's my full solution: https://gmatclub.com/forum/if-a-b-and-c-are-constants-a-b-c-and-x-3-x-x-...

Cheers,
Brent

C = -1

### Yes, that's correct.

Yes, that's correct.

### Could you please explain an

Could you please explain an easier way of tackling question 318 from OG19? It is a sum of cubes question so I was a bit surprised as I thought this was out of scope of GMAT? Anyways, question below for easy reference:

If xy =/ 0, is x^3 + y^3 > 0?
1. x + y > 0
2. xy > 0

### Tricky question!

Tricky question!
Here's my full solution: https://gmatclub.com/forum/if-xy-0-is-x-3-y-268848-20.html#p2637435

By the way, FACTORING sums of cubes is beyond the scope of the GMAT. However, for this question, we need not factor x³ + y³.

### https://gmatclub.com/forum/15

https://gmatclub.com/forum/15-310016.html

so I'm not sure but lowered choices that unit digit is 3.

here is what I do, so 15(15+54) unit digit is 5, (27-22)^2 unit digit is 5, add up to 0 and 63(-63+44) unit digit is -7 so that's why I narrowed down to 33% chances.