第7题=2/猛举禅(2-1)*(2+1)+2/(4-1)*(4+1)+2/(6-1)*(6+1)+2/(8-1)*(8+1)+2/(10-1)*(10+1)+2/(12-1)*(12+1)
=2/1*3+2/3*5+2/5*7+2/7*9+2/9*11+2/11*13
=2/3+2/15+2/35+2/63+2/枝尘99+2/143
=(1-1/3)+(1/3-1/5)+……答尺(1/11-1/13)
=1-1/13
=12/13
为何不把题目写出来呢？
五下数学<一课四练>p76为了优秀怎么做 过程和答案
第7题=2/猛举禅(2-1)*(2+1)+2/(4-1)*(4+1)+2/(6-1)*(6+1)+2/(8-1)*(8+1)+2/(10-1)*(10+1)+2/(12-1)*(12+1)
=2/1*3+2/3*5+2/5*7+2/7*9+2/9*11+2/11*13
=2/3+2/15+2/35+2/63+2/枝尘99+2/143
=(1-1/3)+(1/3-1/5)+……答尺(1/11-1/13)
=1-1/13
=12/13
为何不把题目写出来呢？