SAT数学备考经典模拟题训练32

>>SAT数学模拟题：SAT数学备考经典模拟题训练32

>>SAT考试辅导

练习题内容

· Question #3: What is the value of integer a, if x = 2 is a solution of the equation √(a + x) = 2·x?

(a) a = 10

(b) a = 12

(c) a = 14

(d) a = 16

(e) a = 18

· Question #4: What is the value of (3x + 1 - 3x) / (3x - 3x - 1)?

(a) 6

(b) 3x

(c) 3x + 1

(d) 3x - 1

(e) 3

练习题解析

o Answer: If we square the equation we get a + x = 4·x2

By replacing x with 2, a + 2 = 4·22, so a + 2 = 16.

In conclusion, a = 14.

o Answer: The numerator of the fraction is: 3x + 1 - 3x = 3x·(3 - 1) = 2 · 3x

The denominator of the fraction is: 3x - 3x - 1 = 3x - 1·(3 - 1) = 2 · 3x - 1

We can write the fraction as (2 · 3x) / (2 · 3x - 1) = 3x / 3x - 1 = 3

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