数学篇：SAT考试每日一题 14

>>SAT考试：数学篇：SAT考试每日一题 14

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Read the following SAT test question and then click on a button to select your answer.

Which of the following is equivalent to 4-4a-(5+a)(5-a)?

A.(a-7)(-a+3)

B.(-a+7)(a+3)

C.(a-7)(a+3)

D.(-a+7)(-a+3)

答案：C

解析：

Choice C is correct. First follow the order of operations to get the following.

4-4a-(5+a)(5-a)=4-4a-25+a^2=a^2-4a-21

Since the answer choices do not match this, look for more factors.

The factors of -21 that add to -4 are -7 and 3.

Therefore, the answer is (a-7)(a+3).

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