计算：1-1/3-1/9-1/27-1/81-1/243-1/729
问题描述：
计算：1-1/3-1/9-1/27-1/81-1/243-1/729
答
1-1/3-1/9-1/27-1/81-1/243-1/729
=1-(1/3+1/9+……+1/729)
=1-1/3×[1-(1/3)^6]/(1-1/3)
=1-[1-(1/3)^6]/2
=1-(728/729)/2
=1-364/729
=365/729
括号里面求和，用的是等比数列前n项和公式
答
1-1/3-1/9-1/27-1/81-1/243-1/729
=1-(1/3+1/9+1/27+1/81+1/243+1/729)
=1-(1/3-1/729x1/3)/(1-1/3)
=1-1/2x728/729
=365/729