SAT数学函数练习题及答案解析!SAT数学部分考生可以结合练习掌握考点,为了帮助大家有效的备考,智课网为精选了SAT数学函数练习题,文中有详细的答案解析,方便考生核对。

  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 ['fæktə] n. 因素,因子

  multiple ['mʌltipl] adj. 许多,多种多样的

  equivalent [i'kwivələnt] 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)


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