急求高人解答 数学题!

[1+(1/11+1/13+1/17）]x[(1/11+1/13+1/17)+1/19]
=(1/11+1/13+1/17)+(1/11+1/13+1/17)^2+1/19+(1/11+1/13+1/17)/19
[1+(1/11+1/13+1/17)+1/19]x(1/11+1/13+1/17)
= (1/11+1/13+1/17)+(1/11+1/13+1/17)^2+(1/11+1/13+1/17)/19
原式=1/19