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# One root; Find the value of k

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Senior Manager
Joined: 19 Oct 2010
Posts: 274
Location: India
GMAT 1: 560 Q36 V31
GPA: 3
Followers: 6

Kudos [?]: 42 [0], given: 27

One root; Find the value of k [#permalink]  17 Apr 2011, 08:17
00:00

Difficulty:

25% (medium)

Question Stats:

100% (01:37) correct 0% (00:00) wrong based on 9 sessions
If one root of the equation 2x^2 + 3x – k = 0 is 6, what is the value of k?

(A) 90
(B) 42
(C) 18
(D) 10
(E) –10
[Reveal] Spoiler: OA

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petrifiedbutstanding

SVP
Joined: 16 Nov 2010
Posts: 1682
Location: United States (IN)
Concentration: Strategy, Technology
Followers: 31

Kudos [?]: 345 [0], given: 36

Re: One root; Find the value of k [#permalink]  17 Apr 2011, 08:26
Because 6 is a root, the following is true :

2* 6^2 + 3*6 - k = 0

=> k = 72 + 18 = 90

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Senior Manager
Joined: 19 Oct 2010
Posts: 274
Location: India
GMAT 1: 560 Q36 V31
GPA: 3
Followers: 6

Kudos [?]: 42 [0], given: 27

Re: One root; Find the value of k [#permalink]  17 Apr 2011, 11:18
wow.. as simple as that. Thanks Subhash.
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petrifiedbutstanding

Manager
Joined: 17 Jan 2011
Posts: 231
Followers: 1

Kudos [?]: 25 [0], given: 4

Re: One root; Find the value of k [#permalink]  17 Apr 2011, 12:33
nice,I used the roots equation
=> 6 = (-3 + sqrt(9+8K))/2*2
=> k = 90
So, A
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Re: One root; Find the value of k   [#permalink] 17 Apr 2011, 12:33
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