2002 AMC 12B Problem 2

Attempt Problem 2 of the 2002 AMC 12B below, then check your answer against the professionally curated solution from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2002 AMC 12B solutions, or check the answer key.

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2.

What is the value of (3x2)(4x+1)(3x2)4x+1 \begin{aligned} &(3x-2)(4x+1) \\ &\quad {}-(3x-2)4x+1 \end{aligned} when x=4?x=4?

00

11

1010

1111

1212

Answer: D
Concepts:algebraic manipulationfactoring
Difficulty rating: 980
Solution:

Factor 3x23x-2 out of the first two terms: (3x2)(4x+1)(3x2)4x+1=(3x2)(4x+14x)+1=3x1. \begin{gathered} (3x-2)(4x+1) \\ {}-(3x-2)4x+1 \\ {}=(3x-2)(4x+1-4x)+1 \\ {}=3x-1. \end{gathered} At x=4x=4 this equals 341=11.3\cdot4-1=11.

Thus, the correct answer is D.

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