Question

tính tổng S=10/56+10/140+10/260+..............+10/1400

Answer 1

S=10/56+10/140+10/260+....+10/1400

S=5/28+5/70+5/130+....+5/700

3S/5=3/4.7+3/7.10+3/10.13+...+3/25.28

3S/5=1/4-1/7+1/7-1/10+1/10-1/13+....+1/25-1/28

3S/5=1/4-1/28

3S/5=3/14

S=3/14.5/3

S=5/14

Vậy S=5/14

Answer 2

S=10/56+10/140+10/260+...........+10/1400

S=5/28+5/70+5/130+........+5/700

3S/5=3/4.7+3/7.10+3/13.10+.........+3/25.28

3S/5=1/4-1/7+1/7-1/10+1/10-1/13+.........+1/25-1/28

3S/5=1/4-1/28

3S/5=3/14

S=3/14.5/3

S=5/14

Answer 3

S=5/28+5/70+5/130+.....+5/700

S=5/4x7+5/7x10+5/10x13+.....+5/25x28

Sx3/5=3/4x7+3/7x10+.......+3/25x28

Sx3/5=1/4-1/7+1/7-1/10+1/10+.....+1/25-1/28

Sx3/5=1/4+(1/7-1/7)+(1/9-1/9)+.....+(!/25-1/25)-1/28

Sx3/5=1/4-1/28

Sx3/5=3/14

S=3/14 : 3/5

S=5/14

Answer 4

Sai Hết rùi

Answer 5

5/14 đó bn 

k mk nha

Answer 6

tai sao lai co 3 vay ban ?

Answer 7

9/70 mới đúng

Answer 8

Nói chung là chẳng biết ai đúng sai nên tự làm mà bài toán trên cũng dễ nhận xét thôi mà

Answer 9

bài này đúng đó tôi cá 100% luôn

Answer 10

Chuẩn Rùi

Answer 11

S = 5/28 +5/70 + 5/130 + .... + 5/700

S = 5/3x(3/4x7 + 3/7x10 +3/10x13 + ... + 3/25x28

S=5/3x(1/4 - 1/7 +1/7 - 1/10 + 1/10 - 1/13 + ...+ 1/25 - 1/28 )

S=5/3x(1/4 - 1/28 )

S= 5/3x3/14

S=5/14

100000000o/o đúng

Answer 12

30/28

Answer 13

\(\frac{5}{14}\) là đúng.

Answer 14

Ta có S=10/56+10/140+10/260+...+10/1400 S=5/28+5/70+5/130+...+5/700 3S/5=3/4.7+3/7.10+3/10.13+...+3/25. 28 3S/5=1/4-1/7+1/7-1/10+1/10-1/13+...+1/25-1/28 S=3/14.5/3 S=5/14 Vậy S=5/14

Answer 15

5/14 là đúngggggggggggggggggggggggggg