tinh
1/1.3+1/2.3+1/3.4+...+1/99.100
Tính A = \(\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{99.100}\right)-\left(\frac{1}{1.3}+\frac{1}{3.5}+...+\frac{1}{97.99}\right)+\left(-2-4-6-...-100\right)+\)\(\left(-1.2-2.3-3.4-...-99.100\right)\)
Tính tổng:
A=1/1.2+1/2.3+1/3.4+...+1/99.100
B= 1/1.3+1/3.5+1/5.7+...+1/99.101
A = 1/1.2 + 1/2.3 + 1/3.4 + .... + 1/99.100
A = 1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 +.....+ 1/99- 1/100
A= 1 - 1/100
A= 99/100
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ghi xong hết rồi
mạng nó rớt, ấn gửi trả lời mà không biết
tong teo
a)A = 1/1.2 + 1/2.3 + 1/3.4 + .... + 1/99.100
A = 1 -1/2+1/2-1/3+1/3-1/4+...+1/99-1/100
Rút gọn ta được :
A= 1 - 1/100
A= 99/100
b) B = 1/1.3+1/3.5+1/5.7+....+1/ 99 .101
B x 2 ta có : 1- 1/3 + 1/3 - 1/5+ 1/5-1/7+...+1/99-1/101
B x2 rút gọn ta được: 1 - 1/ 101
B x 2= 100 / 101
B = 100/ 101 : 2 = 50 / 101
Tính :
\(\frac{1}{1.3}+\)\(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{99.100}\)
Mk cần gấp :v
\(\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+...+\frac{1}{99\cdot100}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{99}-\frac{1}{100}\)
\(=1-\frac{1}{100}\)
\(=\frac{99}{100}\)
Sửa lại đề bài nha bạn:
\(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+.....+\frac{1}{99.100}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-......-\frac{1}{99}+\frac{1}{99}-\frac{1}{100}\)
\(=1-\frac{1}{100}\)
\(=\frac{100}{100}-\frac{1}{100}=\frac{99}{100}\)
Chúc em học tốt nhé!
Xin phép sửa đề 1/1.2 + 1/2.3 + 1/3.4 + 1/4.5 + ... + 1/99.100
= 1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + 1/4 - 1/5 + ... + 1/99 - 1/100
= 1 - 1/100
= 99/100
1.Tính
A=\(\dfrac{1}{1.2}+\dfrac{1}{2.3}+\dfrac{1}{3.4}+.....+\dfrac{1}{99.100}\)
B=\(\dfrac{3}{5.6}+\dfrac{3}{6.7}+\dfrac{3}{7.8}+.....+\dfrac{3}{101.102}\)
C=\(\dfrac{1}{1.2.3}+\dfrac{1}{3.4.5}+\dfrac{1}{5.6.7}\)
D=\(\dfrac{2}{1.3}+\dfrac{2}{3.5}+\dfrac{2}{5.7}+\dfrac{2}{7.9}\)
A=1-1/2+1/2-1/3+1/3-1/4+...+1/99-1/100
A=1-1/100 A=99/100 B= (1/5.6+1/6/7+...+1/101.102).3 B=(1/5-1/6+1/6-1/7+...+1/101-1/102).3 B=(1/5-1/102).3 B=97/170
1) Tính
a) Ta có: \(A=\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+...+\dfrac{1}{99\cdot100}\)
\(=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{99}-\dfrac{1}{100}\)
\(=1-\dfrac{1}{100}=\dfrac{99}{100}\)
Tính các tổng sau
1 :D = 1.3 +2.3+3.4+........+99.100
2 . E= 1.3 +3.5+5.7+.........+97.99
3.F= 2.4 + 4.6+ 6+8+..........+98.1009
4. G=1.4+2.5+3.6+........+97.100
Giúp mình nhé . Mình cần gấp
tính giá trị của biểu thức
a) A=\(\frac{1}{1.2}\) + \(\frac{1}{2.3}\) + \(\frac{1}{3.4}\) + \(\frac{1}{4.5}\) + ...+\(\frac{1}{99.100}\)
b) B= \(\frac{2}{1.3}\)+\(\frac{2}{3.5}\) + \(\frac{2}{5.7}\)+\(\frac{2}{7.9}\) +...+\(\frac{2}{97.99}\)
a) \(A=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{99.100}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{99}-\frac{1}{100}\)
\(=1-\frac{1}{100}\)
\(=\frac{99}{100}\)
b) \(B=\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+...+\frac{2}{97.99}\)
\(=2.\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{97}-\frac{1}{99}\right)\)
\(=2.\left(1-\frac{1}{99}\right)\)
\(=2.\frac{98}{99}\)
\(=\frac{196}{99}=1\frac{97}{99}\)
\(A=\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{99.100}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{99}-\frac{1}{100}\)
\(=1-\frac{1}{100}\)
\(=\frac{99}{100}\)
\(B=\frac{2}{1.3}+\frac{2}{3.5}+...+\frac{2}{97.99}\)
\(=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{97}-\frac{1}{99}\)
\(=1-\frac{1}{99}\)
\(=\frac{98}{99}\)
A=\(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+....+\frac{1}{99.100}\)
=>\(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{99}-\frac{1}{100}\)
=>\(\frac{1}{1}-\frac{1}{100}\)
=>\(\frac{99}{100}\)
B=\(\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+.....+\frac{2}{97.99}\)
=>\(\frac{1}{1}-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+....+\frac{1}{97}-\frac{1}{99}\)
=>\(\frac{1}{1}-\frac{1}{99}\)
=>\(\frac{98}{99}\)
Tính tổng :
B = 1.2 + 2.3 + 3.4 + ... + 99.100
C = 1.3 +2.4 +3.5 + 4.6 + ... + 9.11
B = 1.2+2.3+3.4+...+99.100
B=1.100
B=100
C=1.3+2.4+3.5+4.6+...+9.11
C=1.(2+1)+2.(3+1)+3.(4+1)+4.(5+1)+...+9.(10+1)
C=1.2+1+2.3+1+3.4+1+4.5+1+...+9.10+1
C=(1.2+2.3+3.3+4.5+...+9.10)+(1+1+1+1+..+1)
C=1.10+10
C=10+10
C=20
a) B = 1.2+2.3+3.4+..+99.100
=>3B=1.2.3+2.3.3+3.4.3+...+99.100.3
3B = 1.2.3+2.3.(4-1)+3.4.(5-2)+...+99.100.(101-98)
3B = 1.2.3 + 2.3.4 - 1.2.3 + 3.4.5-2.3.4+...+99.100.101-98.99.100
3B = (1.2.3+2.3.4+3.4.5+..+99.100.101) - (1.2.3+2.3.4+...+98.99.100)
3B = 99.100.101
\(B=\frac{99.100.101}{3}=333300\)
b) C = 1.3+2.4+3.5+4.6+...+9.11
C = (2-1).(2+1)+(3-1).(3+1) + (4-1).(4+1)+(5-1).(5+1)+...+(10-1).(10+1)
C = 22 - 1 + 32 - 1 + 42 - 1 + 52 - 1 +...+102 - 1
C = (22+32+42+52+...+102) -(1+1+...+1)
...
A=1.2+2.3+3.4+..........+99.100
B=1.3+3.5+5.7+...........+97.99
C=1.2.3+2.3.4+............98.99.100
A = 1.2. + 2.3 + 3.4 + ... + 99.100
3A = 1.2.3 + 2.3.(4-1) + ... + 99.100.(101-98)
3A = 1.2.3 + 2.3.4 - 2.3.1 + ... + 99.100.101 - 99.100.98
3A = 99.100.101
3A = 999900
A = 333300
A=1.2+2.3+3.4+...........+99.100
B=1.3+3.5+5.7+............+97.99
C=1.2.3+2.3.4+.............+98.99.100
lấy nick khác hả không qua được mắt tui đâu đồ bất công