4/5x7/9+1=?
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GH
29 tháng 2 2016
1+1+1-3+0-9+8-6+5x7-5+6-9-7-5+4+7
=1+1+1-3+0-9+8-6+35-5+6-9-7-5+4+7
=19
VV
3
H9
HT.Phong (9A5)
CTVHS
28 tháng 7 2023
a) \(2+\dfrac{3}{4}\)
\(=\dfrac{8}{4}+\dfrac{3}{4}\)
\(=\dfrac{8+3}{4}\)
\(=\dfrac{11}{4}\)
b) \(\dfrac{1}{3}+\dfrac{3}{2}-\dfrac{7}{4}\)
\(=\dfrac{4}{12}+\dfrac{18}{12}-\dfrac{21}{12}\)
\(=\dfrac{4+18-21}{12}\)
\(=\dfrac{1}{12}\)
c) \(\dfrac{1}{6}+\dfrac{3}{8}-\dfrac{1}{4}\)
\(=\dfrac{4}{24}+\dfrac{9}{24}-\dfrac{6}{24}\)
\(=\dfrac{4+9-6}{24}\)
\(=\dfrac{7}{24}\)
d) \(\dfrac{5}{12}+\dfrac{3}{8}\times\dfrac{4}{9}\)
\(=\dfrac{5}{12}+\dfrac{3\times4}{8\times9}\)
\(=\dfrac{5}{12}+\dfrac{1}{6}\)
\(=\dfrac{5}{12}+\dfrac{2}{12}\)
\(=\dfrac{7}{12}\)
e) \(\dfrac{4}{5}-\dfrac{1}{5}\times\dfrac{7}{2}\)
\(=\dfrac{4}{5}-\dfrac{1\times7}{5\times2}\)
\(=\dfrac{4}{5}-\dfrac{7}{10}\)
\(=\dfrac{8}{10}-\dfrac{7}{10}\)
\(=\dfrac{8-7}{10}\)
\(=\dfrac{1}{10}\)
f) \(\dfrac{16}{9}-\dfrac{4}{15}:\dfrac{2}{5}\)
\(=\dfrac{16}{9}-\dfrac{4}{15}\times\dfrac{5}{2}\)
\(=\dfrac{16}{9}-\dfrac{4\times5}{15\times2}\)
\(=\dfrac{16}{9}-\dfrac{2}{3}\)
\(=\dfrac{16}{9}-\dfrac{6}{9}\)
\(=\dfrac{16-6}{9}\)
\(=\dfrac{10}{9}\)
28 tháng 7 2023
a: =8/4+3/4=11/4
b: =4/12+18/12-21/12=1/12
c: =4/24+9/24-6/24=7/24
d: =5/12+12/72
=5/12+1/6
=5/12+2/12=7/12
e: =4/5-7/10
=8/10-7/10=1/10
f: =16/9-4/15*5/2
=16/9-20/30
=16/9-2/3
=16/9-6/9=10/9
8 tháng 4 2021
Giải:
A=5/9+2/15-6/9
=(5/9-6/9)+2/15
= -1/9 + 2/15
= 1/45
B=2/7-3/8+4/7+1/7-5/8+5/15
= (2/7+4/7+1/7) + (-3/8-5/8) +1/3
= 1+ (-1) +1/3
=1/3
C=3/5+1/15+1/57+1/3-2/9-3/4-1/36
=9/15+1/15+1/57+19/57-8/36-27/36-1/36
=(9/15+1/15)+(1/57+19/57)+(-8/36-27/36-1/36)
=2/3+20/57+(-1)
=58/57+(-1)
=1/57
D=1/1.2+1/2.3+1/3.4+...+1/99.100
=1/1-1/2+1/2-1/3+1/3-1/4+...+1/99-1/100
=1/1-1/100
=99/100
Câu E mình ko biết làm nhé!
M
21 tháng 7 2017
(1/3x5+1/5x7+....+1/19x21)*x=9/7
(1/3-1/5+1/5-1/7+...+1/19-1/21)*x=9/7
(1/3-1/21)*x=9/7
2/7*x=9/7
=> x=9/7:2/7
=> x=9/2
21 tháng 7 2017
Bạn leminhduc sai rùi @@
Ta xét :
B = \(\frac{1}{3.5}+\frac{1}{5.7}+...+\frac{1}{19.21}\)
2 x B = \(\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{19.21}\)
2 x B = \(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{19}-\frac{1}{21}\)
2 x B = \(\frac{1}{3}-\frac{1}{21}\)=\(\frac{2}{7}\)
B = \(\frac{2}{7}:2\)
B = \(\frac{1}{7}\)
Thay B vào biểu thức ta có :
\(\frac{1}{7}.x=\frac{9}{7}\)
=> x = \(\frac{9}{7}:\frac{1}{7}\)=\(\frac{9}{7}.\frac{7}{1}\)=9
Vậy x = 9
6 tháng 2 2016
b ) Đặt \(A=\frac{5}{1.3}+\frac{5}{3.5}+\frac{5}{5.7}+...+\frac{5}{101.103}\)
\(\Rightarrow A=\frac{5}{2}\left(\frac{5}{1}-\frac{5}{3}+\frac{5}{3}-\frac{5}{5}+....+\frac{5}{101}-\frac{5}{103}\right)\)
\(\Rightarrow A=\frac{5}{2}\left(5-\frac{5}{103}\right)\)
ND
1
15 tháng 6 2016
B = 2/5x7 + 3/7x10 + 4/10x14 + 7/14x21 + 9/21x30
B = 1/5 - 1/7 + 1/7 - 1/10 + 1/10 - 1/14 + 1/14 - 1/21 + 1/21 - 1/30
B = 1/5 - 1/30
B = 6/30 - 1/30
B = 5/30 = 1/6
\(\frac{4}{5}.\frac{7}{9}+1\)
= \(\frac{28}{45}+1\)
= \(\frac{73}{45}\)
ủng hộ nha!
4/5x7x9+1=
28/45+1=
28/45+1/1=
73/45