AMC12 2006 B

AMC12 2006 B · Q2

AMC12 2006 B · Q2. It mainly tests Linear equations, Manipulating equations.

For real numbers $x$ and $y$, define $x\spadesuit y = (x + y)(x - y)$. What is $3\spadesuit(4\spadesuit 5)$?

对实数 $x$ 和 $y$，定义 $x\spadesuit y = (x + y)(x - y)$。$3\spadesuit(4\spadesuit 5)$ 的值是多少？

(A) -72 -72

(B) -27 -27

(D) 24 24

(E) 72 72

Answer

Correct choice: (A)

正确答案：（A）

Solution

$4\spadesuit 5=-9$ $3\spadesuit -9=-72 \Rightarrow \text{(A)}$

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