新SAT官方Daily Practise每日一题数学函数题
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摘要:今天起,本系列将给大家带来SAT官方的每日一练真题,各个项目都有,持续更新,希望大家同步多练习。今天这里分享的是5月19日的数学函数题,一起来练习吧!
答案:C
解析:
A quick look at the answer choices tells us that wewill 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 ofsquares 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 ourfactorization 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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