1/1*3+1/2*4+1/3*5+1/4*6+1/5*71+/6*8+1/7*9+1/8*10=?
问题描述:
1/1*3+1/2*4+1/3*5+1/4*6+1/5*71+/6*8+1/7*9+1/8*10=?
答
=1/2*【(1-1/3)+(1/2-1/4)+(1/3-1/5)+.+(1/8-1/10)】
=1/2*(1+1/2-1/9-1/10)
=1/2*(3/2-19/90)
=1/2*(116/90)
=29/45