If a = - 2 , the largest number in the set \ - 3a, 4a, frac 24a, a^2, 1\ is

AMC 8 1985 Problem 8

AMC8 1985 年第 8 题

表达式与运算★★☆☆☆

If a = - 2 , the largest number in the set

\displaystyle \{ - 3a, 4a, \frac {24}{a}, a^2, 1\}

若 a = -2，集合

\displaystyle \{-3a, 4a, \frac{24}{a}, a^2, 1\}

中最大的数是

正确答案 · Correct Answer

Solution 1

Substituting a = -2 yields

\displaystyle \{ - 3a, 4a, \frac {24}{a}, a^2, 1\} = \{ (-3)(-2), 4(-2), \frac{24}{-2}, (-2)^2, 1 \}= \{ 6, -8, -12, 4, 1 \}

The largest element of this set is therefore 6, that is,

-3a

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