Question

tính b=3/10+3/40+3/88+...+3/340

Answer 1

KQ là 9/20 bạn nha

Chúc bạn học tốt

Answer 2

b = 3/2.5+3/5.8+3/8.11+.....+3/17.20

   = 1/2.5+1/5.8+.......+1/17.20

   = 1/2-1/5+1/5-1/8+......+1/17-1/20

   = 1/2- 1/20

   =     9/20

Answer 3

3/10+3/40+3/88+...+3/340

=>\(\frac{3}{2x5}+\frac{3}{5x8}+\frac{3}{8x11}+...+\frac{3}{17x20}\)

\(=\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{11}+...+\frac{1}{17}-\frac{1}{20}\)

\(=\frac{1}{2}-\frac{1}{20}=\frac{9}{20}\)

Answer 4

giúp mk câu này đi d=1/2+5/6+11/12+...+9899/9900

Answer 5

9/20 bạn nhé

Answer 6

đáp án là \(\frac{9}{20}\)