每日一题

Mathematics

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)

答案和解析

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).