First & Second-Degree Equations

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BlindVision: Master | Next Rank: 500 Posts; Posts: 253; Joined: Fri Dec 26, 2008 8:39 pm; Thanked: 8 times; Followed by:1 members

First & Second-Degree Equations

by BlindVision » Sun Mar 08, 2009 4:25 pm

What is the value of x?

1) -(x + y) = x - y

2) x + y = 2

OA = A

I haven't the slightest idea how the answer came to be?

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Source: Beat The GMAT — Data Sufficiency | Sun Mar 08, 2009 4:25 pm

jochoa: Newbie | Next Rank: 10 Posts; Posts: 1; Joined: Mon Feb 02, 2009 7:46 am; Thanked: 1 times

by jochoa » Sun Mar 08, 2009 5:46 pm

The first equation goes as follows:

-(x+y)=x-y
-x-y=x-y
-y-y=2x
2x=0
x=0 (sufficient)

And the second equation:
x=2-y

depends on value of Y (insufficient)

Javo

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logitech: Legendary Member; Posts: 2134; Joined: Mon Oct 20, 2008 11:26 pm; Thanked: 237 times; Followed by:25 members; GMAT Score:730

Re: First & Second-Degree Equations

by logitech » Sun Mar 08, 2009 7:12 pm

BlindVision wrote:What is the value of x?

1) -(x + y) = x - y

2) x + y = 2

OA = A

I haven't the slightest idea how the answer came to be?

What is X ? and there are two variables, X and Y.

This smells C-trap all over the question. But let's start with the easiest statement, Statement II.

We don't know y, so we can not solve for X. INSUF

Now we are left with A, C and E ( your chance of guessing this question went up from 20% to 33%)

Let's work with statement I)

-(x + y) = x - y

-x-y=x-y ( cancel -y on the both side )

-x=x ; 2x=0 and x=0 we know what X is!!

Remember we dont need to carry on the calculation, so dark red part is not neccesary in GMAT. Once you figure out that you can solve the problem...STOP!