Difference between revisions of "2011 AMC 12A Problems/Problem 23"

(Problem)
(Problem)
Line 4: Line 4:
 
<math>
 
<math>
 
\textbf{(A)}\ 0 \qquad
 
\textbf{(A)}\ 0 \qquad
\textbf{(B)}\ \sqrt{2}1 \qquad
+
\textbf{(B)}\ \sqrt{2}-1 \qquad
 
\textbf{(C)}\ \sqrt{3}-1 \qquad
 
\textbf{(C)}\ \sqrt{3}-1 \qquad
 
\textbf{(D)}\ 1 \qquad
 
\textbf{(D)}\ 1 \qquad

Revision as of 01:02, 13 February 2011

Problem

Let $f(z)= \frac{z+a}{z+b}$ and $g(z)=f(f(z))$, where $a$ and $b$ are complex numbers. Suppose that $\left| a \right| = 1$ and $g(g(z))=z$ for all $z$ for which $g(g(z))$ is defined. What is the difference between the largest and smallest possible values of $\left| b \right|$?

$\textbf{(A)}\ 0 \qquad \textbf{(B)}\ \sqrt{2}-1 \qquad \textbf{(C)}\ \sqrt{3}-1 \qquad \textbf{(D)}\ 1 \qquad \textbf{(E)}\ 2$

Solution

See also

2011 AMC 12A (ProblemsAnswer KeyResources)
Preceded by
Problem 22
Followed by
Problem 24
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