(3x + 2) (2x - 5) = ax² + kx + n . What is the value of a

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(3x + 2) (2x - 5) = ax² + kx + n . What is the value of a - n + k ?

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Math Expert

Joined: 02 Sep 2009

Posts: 53066

(3x + 2) (2x - 5) = ax² + kx + n . What is the value of a - n + k ? [#permalink]

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12 May 2016, 00:45

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(3x + 2) (2x - 5) = ax^2 + kx + n . What is the value of a - n + k ?

A. 5
B. 8
C. 9
D. 10
E. 11

Spoiler: OA

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Re: (3x + 2) (2x - 5) = ax² + kx + n . What is the value of a - n + k ? [#permalink]

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12 May 2016, 07:04

Bunuel wrote:

(3x + 2) (2x - 5) = ax^2 + kx + n . What is the value of a - n + k ?

A. 5
B. 8
C. 9
D. 10
E. 11

Simplify LHS..
\((3x+2)(2x-5) = 6x^2-11x-10 = ax^2-n+k\)...
equate the coefficients...
a=6 ; k = -11 and n = -10..
so \(a-n+k = 6-(-10)+(-11) = 6+10-11 = 5\)
A
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Re: (3x + 2) (2x - 5) = ax² + kx + n . What is the value of a - n + k ? [#permalink]

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13 May 2016, 00:13

Bunuel wrote:

(3x + 2) (2x - 5) = ax^2 + kx + n . What is the value of a - n + k ?

A. 5
B. 8
C. 9
D. 10
E. 11

Expanding we have 6x^2 - 15x + 4x -10
6x^2 - 11x - 10

Taking coefficients, a = 6, k= -11, n = -10

Therefore a - n + k = 6 - (-10) - 11 = 16 - 11 = 5

The answer is A.

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Re: (3x + 2) (2x - 5) = ax² + kx + n . What is the value of a - n + k ? [#permalink]

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02 Feb 2019, 17:47

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