tính a=4/2.5 + 4/5.8 + 4/8.11 + … + 4/299.302 giúp em vs ạ

2 bình luận về “tính a=4/2.5 + 4/5.8 + 4/8.11 + … + 4/299.302 giúp em vs ạ”

1.    a=4/(2.5) + 4/(5.8) + 4/(8.11) + … + 4/(299.302)

   = 4.( 1/(2.5) + 1/(5.8) + 1/(8.11)+…+1/(299.302) )

   = 4.[ 1/3 . ( 1/2 – 1/5 + 1/5 – 1/8 + 1/8 – 1/11+…+ 1/299- 1/302)]

   = 4/3 . ( 1/2 – 1/302)

   = 4/3 . 75/141

   = 100/151

   Vậy, a=100/151

   *** $2k10kaitokid$

   Trả lời
2. Lời giải:

   A=4/2.5+4/5.8+4/8.11+…+4/299.302

   A=4/3(3/2.5+3/5.8+3/8.11+…+3/299.302)

   A=4/3(1/2-1/5+1/5-1/8+1/8-1/11+…+1/299-1/302)

   A=4/3(1/2-1/302)

   A=4/3. 75/151

   A=100/151

   Vậy A=100/151

   Trả lời