a^2-3a+1=0除以a得 a-3+1/a=0a+1/a=3a²+1/a²=(a+1/a)²-2=3²-2=7(a-1/a)²=a²+1/a²-2=7-2=5
由aa-3a+1得aa+1=3aa+(1/a)=(aa+1)/a=3a/a=3aa+1/aa=(a+1/a)^2-2×a×1/a=3^2-2=7(a-1/a)^2=a^2-2×a×1/a+1/a^2=7-2=5