Tính tổng :
H= 10/56 + 10/140 + 10/260 + ... + 10/1400
tính tổng M=\(\dfrac{10}{56}+\dfrac{10}{140}+\dfrac{10}{260}+....+\dfrac{260}{1400}\)
Tính tổng : 10/56 + 10/140 + 10/260...+10/1400
Đặt S= 5/28 + 5/70 + 5/130 +.....+5/700
= 5/4.7 + 5/7.10 + ......+ 5/ 25.28
3S/5=1/4-1/7+1/7-1/10+.....+1/25-1/28
3S/5=1/4-1/28
3S/5=3/14
3S=3/14x5
3S=15/14
S=15/14x1/3
S=15/42
tính tổng S=10/56+10/140+10/260+..............+10/1400
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
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
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
Tính tổng: M=10/56+10/140+10/260+...+10/1400
M=10/56+10/140+10/260+...+10/1400
=5/28+5/70+5/130+...+5/700
=5/4.7+5/7.10+5/10.13+...+5/25.28
=5/3(3/4.7+3/7.10+3/10.13+...+3/25.28)
=5/3(1/4-1/7+1/7-1/10+1/10-1/1+...+1/25-1/28)
=5/3.(1/4-1/28)
=5/3.3/14
=5/14
\(\frac{5}{14}\) Là đúng đó bn
nhớ k cho mình nha! hjhj
Tính tổng A=10\56+10\140+10\260+..+10\1400
\(A=\frac{10}{56}+\frac{10}{140}+\frac{10}{260}+...+\frac{10}{1400}\)
\(A=\frac{5}{28}+\frac{5}{70}+\frac{5}{130}+...+\frac{5}{700}\)
\(\frac{3A}{5}=\frac{3}{4\times7}+\frac{3}{7\times10}+\frac{3}{10\times13}+...+\frac{3}{25\times28}\)
\(\frac{3A}{5}=\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+\frac{1}{10}-\frac{1}{13}+...+\frac{1}{25}-\frac{1}{28}\)
\(\frac{3A}{5}=\frac{1}{4}-\frac{1}{28}\)
\(\frac{3A}{5}=\frac{3}{14}\)
\(A=\frac{3}{14}\times\frac{5}{3}\)
\(A=\frac{5}{14}\)
1, Tính tổng
A= 10/56 + 10/140 + 10/260 +....+ 10/1400
@py. Hello, hihi
Tính tổng một cách hợp lý:
M = 10/56 + 10/140 + 10/260 + ... + 10/1400
M=5/28+5/70+...+5/700=5/4.7+5/7.10+...+5/25.28=>3M=5(1/4-1/7+1/7-1/10+...+1/25-1/28)
=>3M=5(1/4-1/28)=>3M=15/14=>M=5/14
Đầu tiên rút gọn M trước
M= 5/28 + 5/70 +.....+10/700
= 5/(4.7)+5/(7.10)+....5/(25.28)
3M= 5( 1/4 - 1/7 +1/7-1/10+......+1/25-1/28)
3M= 5 (1/4-1/28)
3M=15/14
M= 5/14 :D
M=10/56+10/140+10/260+...+10/1400
=5/28+5/70+5/130+...+5/700
=5/(4.7)+5/(7.10)+5/(10.13)+...+5/(25.28)
=(7-4)/(4.7)+(10-7)/(7.10)+(13-10)/(10.13)+...+(28-25)/(25.28)
=3/(4.7)+3/(7.10)+3/(10.13)+...+3/(25.28)
Rồi ta chuyển tử số thành 1
=1/4-1/7+1/7-1/10+1/10-1/13+...+1/25-1/28
=1/4-1/28
=3/14
Tính các tổng sau: H= 10/56+10/140+10/260+............+10/1400
H=10/56+10/140+10/260+....+10/1400
H=5/28+5/70+5/130+....+5/700
3H/5=3/4.7+3/7.10+3/10.13+...+3/25.28
3H/5=1/4-1/7+1/7-1/10+1/10-1/13+....+1/25-1/28
3H/5=1/4-1/28
3H/5=3/14
H=3/14.5/3
H=5/14
Vậy H=5/14
H = 10/56+10/140+10/260+10/1400