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

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== Problem ==
 
== Problem ==
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Let <math>f(z)= \frac{z+a}{z+b}</math> and <math>g(z)=f(f(z))</math>, where <math>a</math> and <math>b</math> are complex numbers. Suppose that <math>\left| a \right| = 1</math> and <math>g(g(z))=z</math> for all <math>z</math> for which <math>g(g(z))</math> is defined. What is the difference between the largest and smallest possible values of <math>\left| b \right|</math>?
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<math>
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\textbf{(A)}\ 0 \qquad
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\textbf{(B)}\ \sqrt{2}1 \qquad
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\textbf{(C)}\ \sqrt{3}-1 \qquad
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\textbf{(D)}\ 1 \qquad
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\textbf{(E)}\ 2 </math>
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== Solution ==
 
== Solution ==
 
== See also ==
 
== See also ==
 
{{AMC12 box|year=2011|num-b=22|num-a=24|ab=A}}
 
{{AMC12 box|year=2011|num-b=22|num-a=24|ab=A}}

Revision as of 02:37, 10 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