Toán nhé>>>>.....

Question

a)A=7/3.13+7/13.23+7/23.33+7/33.43+7.43.53+7/53.63

b)B=1/2+1/6+1/12+1/20+1/30+1/42

Answer 1

a)A=7/3.13+7/13.23+7/23.33+7/33.43+7.43.53+7/53.63

   A=7 (1/3.13 + 1/13.23 + 1/23. 33 + 1/33.43 + 1/43.53 + 1/53.63)

   A=7/10 ( 1/3 - 1/13 + 1/13 -1/23 + 1/23 - 1/33 + 1/33 -1/43 + 1/43 -1/53 + 1/53 - 1/63)

   A=7/10 ( 1/3 - 1/63 )

   A=7/30 -7/630

   A=7/30 - 1/90

   A=15/90 

   A=1/6

b)B=1/2+1/6+1/12+1/20+1/30+1/42

   B=1/1.2 + 1/2.3 + 1/3.4 + 1/4.5 + 1/5.6 + 1/6.7

   B=1- 1/2 + 1/2 -1/3 + 1/3 - 1/4 + 1/4 -1/5 +1/5 - 1/6 + 1/6 -1/7

   B=1 - 1/7

   B=6/7

Tick nha!!!!!!!!!!