BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

(x) = x + 1

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 88
Joined: Tue Mar 03, 2009 8:10 am
Thanked: 3 times

(x) = x + 1

by quocbao » Wed Mar 25, 2009 4:03 am
For any integer x, (x) is defined by the equitation (x) = x + 1. Which of the following is equal to (x)*2 - (x^2) for all integers x

A. 0
B. 2
C. (2x)
D. 2x
E. 2*(x)

[spoiler]OA is D , but why D. I think it should be (x)^2[/spoiler]
Top
Source: — Problem Solving |
Senior | Next Rank: 100 Posts
Posts: 92
Joined: Wed Mar 25, 2009 12:13 pm
Thanked: 10 times

by moutar » Wed Mar 25, 2009 12:39 pm
(x)*2 - (x^2)
= 2[x+1] - [x^2+1]
= 2x + 2 - x^2 -1
= -x^2 + 2x + 1

If the question was (x)^2 - (x^2) then:

(x)^2 - (x^2)
= [x+1]^2 - [x^2+1]
= x^2 + 2x + 1 - x^2 - 1
= 2x
Top
Senior | Next Rank: 100 Posts
Posts: 88
Joined: Tue Mar 03, 2009 8:10 am
Thanked: 3 times

by quocbao » Fri Mar 27, 2009 9:49 am
Oh, I got it. thanks

darn the question
Top
Post new topic Post Reply
• Page 1 of 1