一个一个算:
an+a(n+2)+an*a(n+2)=1;a1=1/2,a2=1/4;
a(n+2)=(1-an)/(1+an)
a3=(1-a1)/(1+a1)=(1-1/2)/(1+1/2)=1/3;
a4=(1-a2)/(1+a2)=(1-1/4)/(1+1/4)=3/5;
a5=(1-a3)/(1+a3)=(1-1/3)/(1+1/3)=1/2;
a6=(1-a4)/(1+a4)=(1-3/5)(1+3/5)=1/4;
a5+a6=1/2+1/4=3/4
一个一个算:
an+a(n+2)+an*a(n+2)=1;a1=1/2,a2=1/4;
a(n+2)=(1-an)/(1+an)
a3=(1-a1)/(1+a1)=(1-1/2)/(1+1/2)=1/3;
a4=(1-a2)/(1+a2)=(1-1/4)/(1+1/4)=3/5;
a5=(1-a3)/(1+a3)=(1-1/3)/(1+1/3)=1/2;
a6=(1-a4)/(1+a4)=(1-3/5)(1+3/5)=1/4;
a5+a6=1/2+1/4=3/4