（1-1⼀4）(1-1⼀9)(1-1⼀16)……(1-1⼀100)

（1-1/4）(1-1/9)(1-1/16)……(1-1/100)
=（1+1/2）（1-1/2)（1+1/3）(1-1/3)（1+1/4）(1-1/4)……（1+1/100）(1-1/100)
=3/2×4/3×5/4×……×101/100×1/2×2/3×3/4×……×99/100
=101/2×1/100
=101/200

11/20
=(2*2-1)/2*2 * (3*3-1)/3*3 * (4*4-1)/4*4 * ... * ((n-1)(n-1)-1)/(n-1)*(n-1) * (n*n-1)/n*n
=(2+1)(2-1)/2*2 * (3+1)(3-1)/3*3 * (4+1)(4-1)/4*4 * ... * ((n-1)+1)((n-1)-1)/(n-1)*(n-1) * (n+1)(n-1)/n*n
=3/2*1/2 * 4/3*2/3 * 5/4*3/4 * ... * n/(n-1)*(n-2)/n-1 * (n+1)(n-1)/n*n
=1/2 * (n+1)/n
=(n+1)/2n
=(10+1)/2*10
=11/20