Difference between revisions of "2006 AMC 12B Problems/Problem 2"

Revision as of 22:12, 9 February 2008

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

$\text {(A) } - 72 \qquad \text {(B) } - 27 \qquad \text {(C) } - 24 \qquad \text {(D) } 24 \qquad \text {(E) } 72$

$4\spadesuit 5=-9$

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

2006 AMC 12B (Problems • Answer Key • Resources)
Preceded by Problem 1	Followed by Problem 3
1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25
All AMC 12 Problems and Solutions

@@ Line 7: / Line 7: @@
 <math>4\spadesuit 5=-9</math>
-<math>3\spadesuit -9=-72 \Rightarrow \text{(B)}</math>
+<math>3\spadesuit -9=-72 \Rightarrow \text{(A)}</math>
 == See also ==
 {{AMC12 box|year=2006|ab=B|num-b=1|num-a=3}}