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If (t 8) is a factor of t^2  kt  48, then k= [#permalink]
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24 Jan 2014, 03:53
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Re: If (t 8) is a factor of t^2  kt  48, then k= [#permalink]
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24 Jan 2014, 03:53




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Re: If (t 8) is a factor of t^2  kt  48, then k= [#permalink]
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24 Jan 2014, 05:55
Factoring the expression: (t  8) (t  ?), since (t  8) is a factor, the other bracket has to be (t + 6). The net result is 2. So (B)? Not sure of the answer because I got lost with the signs a bit.



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Re: If (t 8) is a factor of t^2  kt  48, then k= [#permalink]
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24 Jan 2014, 23:27
Put the value of t8=0, or t=8 in equation t^2+kt+48=0: Solving we get k=2.



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If (t 8) is a factor of t^2  kt  48, then k= [#permalink]
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Updated on: 01 Nov 2014, 03:02
If (t 8) is a factor of \(t^2  kt  48\), then k=
(A)  6 (8)  2 (C) 2 (0) 6 (E) 14
It is given that \((t  8)\) is a factor of the quadratic expression \(t^2  kt  48\) Hence, we need to find the other factor of \(48\) such that the sum of factors is\((\frac{k}{1})=k\).
Thus, \((8) * x = 48\) Or, \(x = 6\)
So, \(k = 8 + ( 6) = 2\)
Answer: (C)
Originally posted by arunspanda on 25 Jan 2014, 00:46.
Last edited by arunspanda on 01 Nov 2014, 03:02, edited 1 time in total.



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Re: If (t 8) is a factor of t^2  kt  48, then k= [#permalink]
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25 Feb 2014, 19:44
8 x ?? = 48 ?? = 6, so the other factor is 6 (t 8)(t +6) would be the two factors k = 8+6 k = 2 k=2 Answer = C
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If (t 8) is a factor of t^2  kt  48, then k= [#permalink]
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Updated on: 11 Nov 2015, 21:45
Vieta's formulas applied to quadratic: x1+x2= b/a & x1*x2=c/a From what is given in the question: 8+x2=k and 8*x2=48 so, x2=6 and thus 8+6=k i.e. k=2
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Re: If (t 8) is a factor of t^2  kt  48, then k= [#permalink]
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30 Jun 2015, 22:27
since (t8) is a factor, then: (8)^2  8k  48 = 0, 8k = 16 k = 2.
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Re: If (t 8) is a factor of t^2  kt  48, then k= [#permalink]
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15 May 2016, 11:04
In this question, I didn't understand this step:
(t−8)(t−8) is a factor of t2−kt−48t2−kt−48 means that t=8t=8 is a solution of the equation t2−kt−48=0t2−kt−48=0.
Why do we assume both equations are equal to 0? What is the rationale of this step? It would be great if someone could explain with examples, or with videos.



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Re: If (t 8) is a factor of t^2  kt  48, then k= [#permalink]
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03 Feb 2017, 03:00
gjonrexha wrote: If (t8) is a factor of t^2  kt  48, then k =
A(6) B(2) C(2) D(6) E(14)
Can someone explain how the answer isnt 6?
(t8)(t+6) = t^2  14 48 >Your red part is somewhat mistake; you can't find (t8)(t+6) = t^2  14 48. Actually, (t8)(t+6)=t^22t48. ***Can someone explain how the answer isnt 6? >if you put put the value of k=6 in t^2  kt  48, then you can't find (t8) as a factor. So, that's why it wrong. But, if k=2, then t^2  kt  48=t^2  2t  48=>t^8t+6t48=>t(t8)+6(t8)=> (t8) (t+6). So, the green part is the factor according to question stem.
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Re: If (t 8) is a factor of t^2  kt  48, then k= [#permalink]
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03 Feb 2017, 20:13
gjonrexha wrote: If (t8) is a factor of t^2  kt  48, then k =
A(6) B(2) C(2) D(6) E(14)
Can someone explain how the answer isnt 6?
(t8)(t+6) = t^2  14 48 We were asked to find the value of k but not the factors of the given expression. 6 will be a factor of the expression, apart from 8. If you want to know k, substitute 8 in the value of t or 6, both will give you the value of K as 2. Here by using 8 directly, gives us the result quicker. Hope this helps
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Re: If (t 8) is a factor of t^2  kt  48, then k= [#permalink]
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08 Feb 2017, 19:39
Bunuel wrote: The Official Guide For GMAT® Quantitative Review, 2ND EditionIf (t 8) is a factor of t^2  kt  48, then k= (A)  6 (B)  2 (C) 2 (D) 6 (E) 14 Since (t  8) is a factor of t^2  kt  48, t = 8 must be a root of the equation t^2  kt  48 = 0. We can substitute 8 for t and determine a value for k. 8^2  8k  48 = 0 64  8k = 48 8k = 16 k = 2 Answer: C
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Re: If (t 8) is a factor of t^2  kt  48, then k= [#permalink]
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23 May 2017, 21:41
Bunuel wrote: The Official Guide For GMAT® Quantitative Review, 2ND EditionIf (t 8) is a factor of t^2  kt  48, then k= (A)  6 (B)  2 (C) 2 (D) 6 (E) 14 Problem Solving Question: 57 Category: Algebra Seconddegree equations Page: 69 Difficulty: 600 GMAT Club is introducing a new project: The Official Guide For GMAT® Quantitative Review, 2ND Edition  Quantitative Questions ProjectEach week we'll be posting several questions from The Official Guide For GMAT® Quantitative Review, 2ND Edition and then after couple of days we'll provide Official Answer (OA) to them along with a slution. We'll be glad if you participate in development of this project: 1. Please provide your solutions to the questions; 2. Please vote for the best solutions by pressing Kudos button; 3. Please vote for the questions themselves by pressing Kudos button; 4. Please share your views on difficulty level of the questions, so that we have most precise evaluation. Thank you! This problem is a good one in a few ways because it has a trap that's useful to learn from and it can be solved in two ways. The simplest method is to realize that t = 8 is a root of the quadratic (as given), plug it into the equation and solve for k directly. 8^2  k(8)  48 = 0 K =2 The other method involves breaking up the quadratic into its roots: (t8)(t+6) = 0 Kt = 8t + 6t by FOIL k = 2 k = 2 However, it's common to set kt = 2t and thus set oneself up for the trap k = 2, one of the answer choices. So it's important to remember that kt is an entire term, not just kt itself, so you need to set the entire term = 2t.



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Re: If (t 8) is a factor of t^2  kt  48, then k= [#permalink]
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26 Aug 2017, 12:22
Bunuel wrote: The Official Guide For GMAT® Quantitative Review, 2ND EditionIf (t 8) is a factor of t^2  kt  48, then k= (A)  6 (B)  2 (C) 2 (D) 6 (E) 14 Problem Solving Question: 57 Category: Algebra Seconddegree equations Page: 69 Difficulty: 600 GMAT Club is introducing a new project: The Official Guide For GMAT® Quantitative Review, 2ND Edition  Quantitative Questions ProjectEach week we'll be posting several questions from The Official Guide For GMAT® Quantitative Review, 2ND Edition and then after couple of days we'll provide Official Answer (OA) to them along with a slution. We'll be glad if you participate in development of this project: 1. Please provide your solutions to the questions; 2. Please vote for the best solutions by pressing Kudos button; 3. Please vote for the questions themselves by pressing Kudos button; 4. Please share your views on difficulty level of the questions, so that we have most precise evaluation. Thank you! hello Bunuel hope my solution finds you well! I would appreciate if you could let me know if my solution is correct! t8 = k t = k+8 Plug in T into t^2  kt – 48  k^2+8^2 – k(k+8) – 48 k^2+8^2 – K^28k– 48 After i eliminate k^2; and – K^2 I get this 648k48 8k= 64+48 8k= 16 then k = 2
Ans K = 2




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