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If x + 3 is a factor of x2 - tx - 12, then t =
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21 Feb 2022, 07:30
21 Feb 2022, 07:30
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Question Stats:
60% (00:34) correct
40% (00:34) wrong based on 5 sessions
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If x + 3 is a factor of \(x^2 - tx - 12\), then t =
(A) -4
(B) -1
(C) 1
(D) 3
(E) 5
(A) -4
(B) -1
(C) 1
(D) 3
(E) 5
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Joined: 09 Nov 2021
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Re: If x + 3 is a factor of x2 - tx - 12, then t =
[#permalink]
21 Feb 2022, 09:30
21 Feb 2022, 09:30
1
In this case, we are given one side of a broken quadratic and not the other. We know that x+3 is one side of this broken quadratic, however, and can therefore infer the other side: x-4.
I know that it has to be -4 because the +3 and -4 must multiply to give -12.
Therefore, we multiply the two to find t: (x+3)(x-4) = x^2 -4x + 3x - 12 = x^2 - 1x -12.
Be careful here that the sign is correct: remember, in the given equation we have -t in front of the x in the middle. That implies that -t = -1, or t = 1. Answer C.
I know that it has to be -4 because the +3 and -4 must multiply to give -12.
Therefore, we multiply the two to find t: (x+3)(x-4) = x^2 -4x + 3x - 12 = x^2 - 1x -12.
Be careful here that the sign is correct: remember, in the given equation we have -t in front of the x in the middle. That implies that -t = -1, or t = 1. Answer C.
gmatclubot
Re: If x + 3 is a factor of x2 - tx - 12, then t = [#permalink]
21 Feb 2022, 09:30
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