第 5 題
\(\begin{align}
  & f\left( x \right)={{\left( \frac{a}{c} \right)}^{x}}+{{\left( \frac{b}{c} \right)}^{x}} \\
& {{a}^{n}}+{{b}^{n}}={{c}^{n}} \\
& f\left( n \right)=1 \\
&  \\
& \frac{a}{c}<1,\frac{b}{c}<1 \\
& {{\left( \frac{a}{c} \right)}^{2}}+{{\left( \frac{b}{c} \right)}^{2}}=f\left( 2 \right)>f\left( n \right)=1 \\
& {{a}^{2}}+{{b}^{2}}>{{c}^{2}} \\
\end{align}\)
銳角三角形

第 10 題
\(k = 20000U_1\)，由於\(U_1\)是正整數，故\(k\)有無限多個
還是有遺漏條件？

第4題
\(\left( \frac{{{x}^{2}}}{x+2}+\frac{{{y}^{2}}}{y+1} \right)\left( x+2+y+1 \right)\ge {{\left( x+y \right)}^{2}}\)

\(\sqrt{74}\)那裡應是\(5\sqrt{2}\)，答案是\(5+5\sqrt{2}\)