用乘法公式计算 谢谢

=[(2^2-1)*(3^2-1)*(4^2-1)*(5^2-1)*(6^2-1)*(7^2-1)*(8^2-1)*(9^2-1)*(10^2-1)]/[(2*3*4*5*6*7*8*9*10)^2]
=[4-1)(9-1)(16-1)(25-1)(36-1)(49-1)(64-1)(81-1)(100-1)]/(4*9*16*25*36*49*64*81*100)
=(3*8*15*24*35*48*63*80*99)/(4*9*16*25*36*49*64*81*100)
=11/20
=0.55

=(2+1)*(2-1)*(3+1)*(3-1)...(10+1)*(10-1)*1/4*1/9*1/16*1/100
=11/20

=(1-1/2)(1+1/2)(1-1/3)(1+1/3)(1-1/4)(1+1/4)......(1+1/9)(1-1/10)(1+1/10) 算术平方差公式
=1/2*3/2*2/3*4/3*4/3*5/4*......*10/9*9/10*11/10
=1/2*11/10 每个的后一项与下个的前一项乘积为1
=11/20