1+1/2+4+1/2+4+6+1/2+4+6+8+.+1/2+4+6+8...+20

是不是 1+1/(2+4)+1/(2+4+6)+1/(2+4+6+8)+.+1/(2+4+6+8...+20)=?嗯1+1/(2+4)+1/(2+4+6)+1/(2+4+6+8)+...+1/(2+4+6+8...+20)
=1+1/(2×3)+1/(3×4)+1/(4×5) +1/(5×6)+…+1/(10×11)
=1+1/2-1/3+1/3-1/4+… +1/10-1/11
=1-1/11
=10/11答案出错把？先看方法懂了吗？
你原题第一项一个是：1/2
1/2+1/(2+4)+1/(2+4+6)+1/(2+4+6+8)+...+1/(2+4+6+8...+20)
=1/2+1/2+1/(2×3)+1/(3×4)+1/(4×5) +1/(5×6)+…+1/(10×11)
=1-1/2+1/2-1/3+1/3-1/4+… +1/10-1/11
=1-1/11
=10/11
如果不改题：
1+1/(2+4)+1/(2+4+6)+1/(2+4+6+8)+...+1/(2+4+6+8...+20)
=1+1/(2×3)+1/(3×4)+1/(4×5) +1/(5×6)+…+1/(10×11)
=1+1/2-1/3+1/3-1/4+… +1/10-1/11
=1+1/2-1/11
=10/11+1/2
=31/22