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If x^2 + 2x − 24 = 24, which of the following is a potential value of

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Bunuel
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If x^2 + 2x − 24 = 24, which of the following is a potential value of [#permalink] New post   13 May 2018, 21:24
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A
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If x^2 + 2x − 24 = 24, which of the following is a potential value of x?

A. -6
B. 0
C. 4
D. 6
E. 8
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D
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Re: If x^2 + 2x − 24 = 24, which of the following is a potential value of [#permalink] New post   13 May 2018, 21:36
Solving the quadratic equation:
x^2 + 2x − 48 = 0
x^2 + 8x - 6x - 48 = 0
x*(x+8) -6*(x + 8) = 0
x = -8 or 6
Hence, Answer is D
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Re: If x^2 + 2x − 24 = 24, which of the following is a potential value of [#permalink] New post   14 May 2018, 08:04
Quadratic equation = answer = D
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Re: If x^2 + 2x − 24 = 24, which of the following is a potential value of [#permalink] New post   14 May 2018, 08:14
Bunuel wrote:
If x^2 + 2x − 24 = 24, which of the following is a potential value of x?

A. -6
B. 0
C. 4
D. 6
E. 8


I have tried an easier way to solve this question.

\(x^2 + 2x − 24 = 24\)

\(x^2 + 2x = 24 + 24\)

x (x+2) = 48.

Substitute each option.
Clearly 6 (6+2) = 48. x =6

Ans - D

Please let me know if I am missing anything.
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Re: If x^2 + 2x − 24 = 24, which of the following is a potential value of [#permalink] New post   14 May 2018, 08:46
Bunuel wrote:
If x^2 + 2x − 24 = 24, which of the following is a potential value of x?

A. -6
B. 0
C. 4
D. 6
E. 8

\(x^2 + 2x - 48 = 0\)

Or, \(x^2 + x(8 - 6) - 48 = 0\)

Or, \(x^2 + x - 6x - 48 = 0\)

Or, \(x(x + 8) - 6(x + 8)= 0\)

Or, \((x - 6)(x + 8) = 0\)

Or, x = 6 and x = -8, Thus Answer must be (D)
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Re: If x^2 + 2x − 24 = 24, which of the following is a potential value of [#permalink] New post   14 Jul 2018, 19:13
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Bunuel wrote:
If x^2 + 2x − 24 = 24, which of the following is a potential value of x?

A. -6
B. 0
C. 4
D. 6
E. 8


Simplifying the equation, we have:

x^2 + 2x - 48 = 0

(x + 8)(x - 6) = 0

x = -8 or 6

Answer: D
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Re: If x^2 + 2x − 24 = 24, which of the following is a potential value of [#permalink]
14 Jul 2018, 19:13
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