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Intern
Joined: 28 Feb 2011
Posts: 35

Kudos [?]: 7 [0], given: 1

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06 May 2011, 19:27
Hi Guys,

I came across the below problem in a gmat online practice test..can anybody pls provide
suggestions to solve the problem?

If a+b+2ac =0 are the roots of the equation ax^2 +bx +c = 0 then which of the following is true?

a+b+2ac = 0
a^2+b^2+2ac=0
a-b+2ac =0
a^2-b^2+2ac = 0
none of these

My approach is :

formula for finding roots of a quadratic equation is -b +/- SQRT(b^2-4ac)/2a

a+b+2ac = -b +/- SQRT(b^2-4ac)/2a

a+2ac +b = -b +/- SQRT(b^2-4ac)/2a

a(1+2c) +b = -b +/- SQRT(b^2-4ac)/2a combining like terms on the left hand side eq.

squaring on both sides:

(a(1+2c) +b)^2 = b^2+/- b^2-4ac/4a^2

getting too long here..any suggestions pls?

Anu

Kudos [?]: 7 [0], given: 1

Senior Manager
Joined: 24 Mar 2011
Posts: 443

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Location: Texas

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06 May 2011, 22:50
anuu wrote:
If a+b+2ac =0 are the roots of the equation ax^2 +bx +c = 0 then which of the following is true?

Anu

did not understand the highlighted portion... is it possible to have a+b+2ac=0 as roots?

Kudos [?]: 208 [0], given: 20

Intern
Joined: 28 Feb 2011
Posts: 35

Kudos [?]: 7 [0], given: 1

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07 May 2011, 08:50
I too had the same thought on whetther a+b+2ac (that too with 3 variables) could be the roots...but this os how the question was mentioned in the online practice test.

Is this a typo in the question ?

Anuu

Kudos [?]: 7 [0], given: 1

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