2/[(n)(n+2)]=[1/n-1/(n+2)]
x/x(x+2)+x/(x+2)(x+4)……x/(x+8)(x+10)
=(x/2)[2/x(x+2)+2/(x+2)(x+4)……+2/(x+8)(x+10)]
=(x/2)[1/x-1/(x+2)+1/(x+2)-1/(x+4)……+1/(x+8)-1/(x+10)]
=(x/2)[1/x-1/(x+10)]
x=-5
经过验证
分母没有x+5
所以答案为x=-5