absolute value

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Gurpinder: Legendary Member; Posts: 659; Joined: Mon Dec 14, 2009 8:12 amFollowed by: 3 members; Thanked: 32 times

by Gurpinder » Thu Aug 26, 2010 11:01 am

what are the 2 values for this eq.

22-|y+14|=20

"Do not confuse motion and progress. A rocking horse keeps moving but does not make any progress."
- Alfred A. Montapert, Philosopher.

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Source: Beat The GMAT — Problem Solving | Thu Aug 26, 2010 11:01 am

phillybeat: Junior | Next Rank: 30 Posts; Posts: 15; Joined: Mon Aug 23, 2010 1:52 pm; Thanked: 1 times

by phillybeat » Thu Aug 26, 2010 11:06 am

Gurpinder wrote:what are the 2 values for this eq.

22-|y+14|=20

22-20 = |y+14|
y+14 = 2 or y+14 = -2

answer is -16,-12

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Gurpinder: Legendary Member; Posts: 659; Joined: Mon Dec 14, 2009 8:12 amFollowed by: 3 members; Thanked: 32 times

by Gurpinder » Thu Aug 26, 2010 11:10 am

i get -16, but how did u get -12

"Do not confuse motion and progress. A rocking horse keeps moving but does not make any progress."
- Alfred A. Montapert, Philosopher.

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scorpionz: Senior | Next Rank: 100 Posts; Posts: 98; Joined: Thu Aug 19, 2010 10:00 amFollowed by: 1 member; Thanked: 7 times; GMAT Score:760

by scorpionz » Thu Aug 26, 2010 11:15 am

Gurpinder wrote:i get -16, but how did u get -12

The two eqns can be -
a) 22 - (y+14) = 20
=> 8-y = 20
=> y=-12

b) 22 + (y+14) = 20
=> 36+y = 20
=> y=-16

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BastiG: Master | Next Rank: 500 Posts; Posts: 146; Joined: Sun Jun 13, 2010 5:05 am; Thanked: 7 times

by BastiG » Thu Aug 26, 2010 3:14 pm

You should always try to seperate the absolute value from the rest of the equation.

22-|y+14|=20
--> |y+14|=+2

2 can be either negative or positiv. It is easier if you think of

|y|=2

Now you can visualize

| | |
-2 0 2

--> So y can be either -2 or 2.

If you subtract the number 14. You get:

| | |
-16 -14 -12

--> So y can be either -16 or -12.

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Gurpinder: Legendary Member; Posts: 659; Joined: Mon Dec 14, 2009 8:12 amFollowed by: 3 members; Thanked: 32 times

by Gurpinder » Fri Aug 27, 2010 10:12 am

Ok I see that |y| = +- x

But in this question,

22 - |y+14|=20
--> |y+14|=+2

what happens to the - sign in front of |y+14| ??

"Do not confuse motion and progress. A rocking horse keeps moving but does not make any progress."
- Alfred A. Montapert, Philosopher.

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BastiG: Master | Next Rank: 500 Posts; Posts: 146; Joined: Sun Jun 13, 2010 5:05 am; Thanked: 7 times

by BastiG » Fri Aug 27, 2010 10:28 am

Gurpinder wrote:Ok I see that |y| = +- x

But in this question,

22 - |y+14|=20
--> |y+14|=+2

what happens to the - sign in front of |y+14| ??

Well you can just multiply it by (-1).

22-|y+14|=20
-|y+14|=20-22
-|y+14|=-2 |*(-1)
|y+14|=2

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