每日一题

Mathematics>Standard Multiple Choice

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

(a+3)(2a^2-5a+7)

Which of the following is equivalent to the expression above?

A.2a^3-5a+21
B.2a^3+a^2-8a+21
C.2a^3+6a^2-5a+7
D.2a^3+11a^2+22a+21

答案和解析

答案：B

解析：

Choice B is correct. When multiplying polynomials, be sure to multiply each term in the first polynomial by each term in the second polynomial.

This can be done as follows: (a+3)(2a^2-5a+7)=2a^3-5a^2+7a+6a^2-15a+21

Combine like terms to get:

2a^3+a^2-8a+21

The equivalent expression is 2a^3+a^2-8a+21.