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OG Diag #16. Time consuming Quadratics problem

Expert replies
by tonebeeze » Mon Jan 17, 2011 9:03 pm
This PS quadratics problem on the OG Diagnostic really is a time sapper. Any suggestions regarding the most efficient way to solve these problem types?

If square root{3-2x} = square root{2x} +1, then 4x^2 =
(A) 1
(B) 4
(C) 2 − 2x
(D) 4x − 2
(E) 6x − 1

*How do you add in mathematic symbols into our BTG posts?

OA = E
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Source: — Problem Solving |

by anshumishra » Mon Jan 17, 2011 9:09 pm
tonebeeze wrote:This PS quadratics problem on the OG Diagnostic really is a time sapper. Any suggestions regarding the most efficient way to solve these problem types?

If square root{3-2x} = square root{2x} +1, then 4x^2 =
(A) 1
(B) 4
(C) 2 − 2x
(D) 4x − 2
(E) 6x − 1

*How do you add in mathematic symbols into our BTG posts?

OA = E
Take the square of both sides of the given equation :
3-2x=2x+2√2x+1
=> 2-4x = 2√2x
Again take square, both sides
=> 4 + 16x^2 -16x = 8x
=> 4x^2 -6x +1 = 0
=> 4x^2 = 6x - 1 E
Thanks
Anshu

(Every mistake is a lesson learned )
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by GMATGuruNY » Mon Jan 17, 2011 9:27 pm
tonebeeze wrote:This PS quadratics problem on the OG Diagnostic really is a time sapper. Any suggestions regarding the most efficient way to solve these problem types?

If square root{3-2x} = square root{2x} +1, then 4x^2 =
(A) 1
(B) 4
(C) 2 − 2x
(D) 4x − 2
(E) 6x − 1

*How do you add in mathematic symbols into our BTG posts?

OA = E
√(3-2x) = √2x + 1

[√(3-2x)]² = (√2x + 1)²

3 - 2x = (√2x + 1)(√2x + 1)

3 - 2x = 2x + √2x + √2x + 1

2 - 2x = 2x + 2√2x

1 - x = x + √2x

1 - 2x = √2x

(1 - 2x)² = (√2x)²

(1 - 2x)(1 - 2x) = 2x

1 - 2x - 2x + 4x² = 2x

4x² = 6x - 1.

The correct answer is E.

To insert √ on a PC, hold down the Alt key as you type the numbers 251. Macs have a built-in character viewer that facilitates the insertion of math characters.
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