A+1/A=5(A+1/A)^2=A^2+1/A^2+2=25所以A^2+1/A^2=23(A^4+A^2+1)/A^2=A^2+1/A^2+1=23+1=24
a+1/a=5(a^4+a^2+1)/a^2=a^2+1/a^2+1=(a+1/a)^2-1=5^2-1=24
a+1/a=5(aaaa+aa+1)/aa=aa+1+1/aa=(a+1/a)^2-1=5^2-1=24
