2/1X3+2/3X5+2/5x7+.+2/19x21全过程(最好带原因),
问题描述:
2/1X3+2/3X5+2/5x7+.+2/19x21全过程(最好带原因),
答
=2*(1/1*3+1/3*5+.)=2*1/2*(1-1/3+1/3-1/5.+1/19-1/21)=20/21
2/1X3+2/3X5+2/5x7+.+2/19x21全过程(最好带原因),
=2*(1/1*3+1/3*5+.)=2*1/2*(1-1/3+1/3-1/5.+1/19-1/21)=20/21