依题 意
P1的坐标(1,k) P2的坐标(2,k/2).
A1=1*k/2 A2=2*k/3,.
A1=a 则a=k/2 k=2a
A1×A2×.×An
=1*k/2*2*k/3*3*k/4*.*n*k/(n+1)
=k^n/(n+1)=(2a)^n/(n+1)^是啥意思啊看不懂依题 意P1的坐标(1，k)P2的坐标(2, k/2).....A1=x1y2=1*k/2A2=x2y3=2*k/3, .....A(n-1)=x(n-1)yn=(n-1)*k/n,An=xny(n+1)=n*k/(n+1),A1=a则a=k/2k=2a上面这应看懂吧A1×A2×。。。。A(n-1)×An=1*k/2 * 2*k/3 * 3*k/4 * ......* (n-1)*k/n * n*k/(n+1) k/2 * 2=kk/3 * 3=k......=1*k/2 * 2*k/3 * 3*k/4 * ......* (n-1)*k/n * n*k/(n+1)=k的n次方/（n+1)k=2a=2a的n次方/（n+1)