平方得x2+1/x2=11 即(x+1/x)^2=13,x+1/x=± √13 (1)平方，x4+1/x4=119(1)*(2),得x3+1/x3=±10√13(2)*(3),得x5+1/x5=±109√13 原式=（X5+X3+1/X3+1/x5）/（X5+X+1/X+1/x5）=±119/110
