MathDB
Complex Function

Source: AMC 12 2008B Problem 19

February 29, 2008
functioninequalitiescomplex numberstriangle inequalityAMC

Problem Statement

A function f f is defined by f(z) \equal{} (4 \plus{} i) z^2 \plus{} \alpha z \plus{} \gamma for all complex numbers z z, where α \alpha and γ \gamma are complex numbers and i^2 \equal{} \minus{} 1. Suppose that f(1) f(1) and f(i) f(i) are both real. What is the smallest possible value of | \alpha | \plus{} |\gamma |? <spanclass=latexbold>(A)</span>  1<spanclass=latexbold>(B)</span>  2<spanclass=latexbold>(C)</span>  2<spanclass=latexbold>(D)</span>  22<spanclass=latexbold>(E)</span>  4 <span class='latex-bold'>(A)</span> \; 1 \qquad <span class='latex-bold'>(B)</span> \; \sqrt {2} \qquad <span class='latex-bold'>(C)</span> \; 2 \qquad <span class='latex-bold'>(D)</span> \; 2 \sqrt {2} \qquad <span class='latex-bold'>(E)</span> \; 4 \qquad