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

  Which of the following expressions is equivalent to16x^4-81?

  A.(4x^3-9)(4x+9)

  B.(2x-3)(2x+3)(4x^2-9)

  C.(2x-3)(2x+3)(4x^2+9)

  D.(2x-3)^4

  重点单词：

  factor ['f?kt?] n. 因素，因子

  multiple ['m?ltipl] adj. 许多，多种多样的

  equivalent [i'kwiv?l?nt] adj. 等价的，相等的

  答案：C

  解析：

  A quick look at the answer choices tells us that we will want to factor the given expression.

  Recall that a difference of squares of the form a^2-b^2 factors to (a-b)(a+b).

  Because 16x^4 and 81 are both perfect squares, the expression 16x^4-81 is a

  difference of squares and can be factored as follows: 16x^4-81=(4x^2-9)(4x^2+9)

  Note that the binomial (4x^2-9) also is a difference of squares. Therefore, we can continue our factorization as follows: (4x^2-9)(4x^2+9)=(2x-3)(2x+3)(4x^2+9)

  16x^4-81 is equivalent to: (2x-3)(2x+3)(4x^2+9)

  以上就是SAT数学函数题型，更多相关的资料，请点击：SAT数学频道