Problem:
How many of the following are equal to xx+xx for all x>0?
I: 2xx,II: x2x,III: (2x)x,IV: (2x)2x
Answer Choices:
A. 0
B. 1
C. 2
D. 3
E. 4
Solution:
Only one, namely 2xx, equals xx+xx for all x>0. Use x=2 or x=3 to show that the given expression is not identical to any of the other choices.