遞迴數列: n {\displaystyle n} 為整數, F 1 = F 2 = 1 {\displaystyle F_{1}=F_{2}=1} , F n = F n − 1 + F n − 2 {\displaystyle F_{n}=F_{n-1}+F_{n-2}} 由此可知 F 1 , F 2 , F 3 , ⋯ {\displaystyle F_{1},F_{2},F_{3},\cdots } 依序是1,1,2,3,5,8,13,21...... F 0 {\displaystyle F_{0}} 是0 F − 1 , F − 2 , F − 3 , ⋯ {\displaystyle F_{-1},F_{-2},F_{-3},\cdots } 依序是1,-1,2,-3,5,-8,13,-21...... 請問如何證明「 | ( F n ) 2 − F n − m ⋅ F n + m | = ( F m ) 2 {\displaystyle \left|(F_{n})^{2}-F_{n-m}\cdot F_{n+m}\right|=(F_{m})^{2}} ,其中 m {\displaystyle m} 是非負整數」?謝謝! 例如 n = 12 , m = 7 {\displaystyle n=12,m=7} 時, | ( F 12 ) 2 − F 5 ⋅ F 19 | = | 144 2 − 5 ⋅ 4181 | = 13 2 = ( F 7 ) 2 {\displaystyle \left|(F_{12})^{2}-F_{5}\cdot F_{19}\right|=\left|144^{2}-5\cdot 4181\right|=13^{2}=(F_{7})^{2}} 又例如 n = 4 , m = 10 {\displaystyle n=4,m=10} 時, | ( F 4 ) 2 − F − 6 ⋅ F 14 | = | 3 2 − ( − 8 ) ⋅ 377 | = 55 2 = ( F 10 ) 2 {\displaystyle \left|(F_{4})^{2}-F_{-6}\cdot F_{14}\right|=\left|3^{2}-(-8)\cdot 377\right|=55^{2}=(F_{10})^{2}}