2002 AMC 10B Problem 4

Attempt Problem 4 of the 2002 AMC 10B 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 10B solutions, or check the answer key.

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4.

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:distributive propertyfactoring
Difficulty rating: 900
Solution:

Factoring 3x23x-2 from the first two terms, (3x2)[(4x+1)4x]+1=(3x2)(1)+1=3x1. \begin{aligned} &(3x - 2)\big[(4x + 1) - 4x\big] + 1 \\ &= (3x - 2)(1) + 1 \\ &= 3x - 1. \end{aligned}

At x=4,x = 4, this equals 341=11.3\cdot4 - 1 = 11.

Thus, the correct answer is D.

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