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Re: equation puzzle [#permalink]
16 Dec 2010, 07:31

1

This post received KUDOS

Hi

I guess the answer is 12.

X^2+px+12=0 with one root as 4

ie 4+b=-p where b is another root and 4b=12,then b=3

From second equation X^2+px+q=0 ,as roots are equal ,then first root ie 4 and second root ie b=3 are the roots for second equation as well,making 4*3=q ie 12 Ans E

Re: equation puzzle [#permalink]
16 Dec 2010, 07:42

Expert's post

Eshika wrote:

Hi

I guess the answer is 12.

X^2+px+12=0 with one root as 4

ie 4+b=-p where b is another root and 4b=12,then b=3

From second equation X^2+px+q=0 ,as roots are equal ,then first root ie 4 and second root ie b=3 are the roots for second equation as well,making 4*3=q ie 12 Ans E

It's given that the roots of x^2+px+q=0 are equal (so given that it has double root), not that the roots of this equation equal to the roots of another: x^2+px+12=0. If it were as you say then we would have q=12 right away: x^2+px+q=0; x^2+px+12=0.

Re: equation puzzle [#permalink]
16 Dec 2010, 21:22

Bunuel wrote:

Eshika wrote:

Hi

I guess the answer is 12.

X^2+px+12=0 with one root as 4

ie 4+b=-p where b is another root and 4b=12,then b=3

From second equation X^2+px+q=0 ,as roots are equal ,then first root ie 4 and second root ie b=3 are the roots for second equation as well,making 4*3=q ie 12 Ans E

It's given that the roots of x^2+px+q=0 are equal (so given that it has double root), not that the roots of this equation equal to the roots of another: x^2+px+12=0. If it were as you say then we would have q=12 right away: x^2+px+q=0; x^2+px+12=0.

Re: equation puzzle [#permalink]
18 Dec 2010, 07:25

1

This post received KUDOS

Eshika wrote:

Hi

I guess the answer is 12.

X^2+px+12=0 with one root as 4

ie 4+b=-p where b is another root and 4b=12,then b=3

From second equation X^2+px+q=0 ,as roots are equal ,then first root ie 4 and second root ie b=3 are the roots for second equation as well,making 4*3=q ie 12 Ans E

so the 2 roots of equation are 4 & 3 p = - (4+3) =-7 so 2 eq becomes x^2-7x+q it is given 2 roots of the equation are same a=b a+b =7, 2a=7 a=7/2 q = a^2 = 49/4

Re: equation puzzle [#permalink]
19 Dec 2010, 21:07

feruz77 wrote:

If one root of x^2+px+12=0 is 4, and the equation x^2+px+q=0 has equal roots then the value of q is a) 49/4 b) 4/49 c) 4 d) 1/4 e) 12

Thanks feruz77,I just started using GMAT club and got to know the concept of kudos after getting a mail that I have received 1 kudos.Will start using them now onwards.

Re: If one root of x^2+px+12=0 is 4, and the equation x^2+px+q=0 [#permalink]
27 Sep 2013, 07:59

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Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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