Better way to solve OG p 22 #16

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barcebal: Senior | Next Rank: 100 Posts; Posts: 81; Joined: Wed Jul 07, 2010 2:21 pm; Thanked: 12 times; Followed by:2 members; GMAT Score:760

Better way to solve OG p 22 #16

by barcebal » Mon Jul 12, 2010 9:05 am

I know that you can do the algebra posted in the explanation of the OG, but I'm curious what tips/tricks anyone would have for this question:

If sqrt((3-2x)) = sqrt(2x) + 1, then 4(x^2)= ?

A 1
B 4
C 2-2x
D 4x-2
E 6x-1

I know that you can easily rule out A and B by plugging so what is a fast shortcut to finding the answer?

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Source: Beat The GMAT — Problem Solving | Mon Jul 12, 2010 9:05 am

kvcpk: Legendary Member; Posts: 1893; Joined: Sun May 30, 2010 11:48 pm; Thanked: 215 times; Followed by:7 members

by kvcpk » Mon Jul 12, 2010 10:14 am

barcebal wrote:I know that you can do the algebra posted in the explanation of the OG, but I'm curious what tips/tricks anyone would have for this question:

If sqrt((3-2x)) = sqrt(2x) + 1, then 4(x^2)= ?

A 1
B 4
C 2-2x
D 4x-2
E 6x-1

I know that you can easily rule out A and B by plugging so what is a fast shortcut to finding the answer?

GMAT cannot use imaginary numbers.

So look at options:
4x^2 +2x- 2 = 0
b^2 -4ac <0
So ruled out.

4x^2-4x+2 = 0
b^2 -4ac <0
So ruled out.

4x^2-6x+1=0
b^2-4ac>0

pick E.