Tìm a/b biết: 5/9*a/b-11/21=4/21
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C
21 tháng 5 2022
5/9 x a/b -11/21 = 4/21
\(\dfrac{5}{9}\times\dfrac{a}{b}=\dfrac{4}{21}+\dfrac{11}{21}\)
\(\dfrac{5}{9}\times\dfrac{a}{b}=\dfrac{15}{21}=\dfrac{5}{7}\)
\(\dfrac{a}{b}=\dfrac{5}{7}:\dfrac{5}{9}\)
\(\dfrac{a}{b}=\dfrac{5}{7}\times\dfrac{9}{5}\)
\(\dfrac{a}{b}=\dfrac{9}{7}\)
21 tháng 5 2022
5/9.a/b=4/21+11/21
5/9.a/b=15/21
a/b=15/21:5/9
a/b=15/21.9/5
a/b=9/7
=> a=9 ; b=7
5 tháng 6 2018
Bài 1:
a) \(\frac{16}{15}.\frac{\left(-5\right)}{14}.\frac{54}{24}.\frac{56}{21}\)
\(=\frac{4.2.2}{5.3}.\frac{\left(-5\right)}{2.7}.\frac{3.3}{4}.\frac{8}{3}\)
\(=\frac{4.2.2.\left(-5\right).3.3.8}{5.3.2.7.4.3}\)
\(=\frac{-16}{7}\)
b) \(\frac{7}{3}.\frac{\left(-5\right)}{2}.\frac{15}{21}.\frac{4}{\left(-5\right)}\)
\(=\frac{7}{3}.\frac{\left(-5\right)}{2}.\frac{5}{7}.\frac{2.2}{\left(-5\right)}\)
\(=\frac{7.\left(-5\right).5.2.2}{3.2.7.\left(-5\right)}\)
\(=\frac{10}{3}\)
5 tháng 6 2018
Bài 2:
a) \(\frac{21}{24}.\frac{11}{9}.\frac{5}{7}=\frac{7}{8}.\frac{11}{9}.\frac{5}{7}=\frac{11.5}{8.9}=\frac{55}{72}\)
b) \(\frac{5}{23}.\frac{17}{26}+\frac{5}{23}.\frac{9}{26}\)
\(=\frac{5}{23}.\left(\frac{17}{26}+\frac{9}{26}\right)=\frac{5}{23}.1=\frac{5}{23}\)
c) \(\left(\frac{3}{29}-\frac{1}{5}\right).\frac{29}{3}=\frac{3}{29}.\frac{29}{3}-\frac{1}{5}.\frac{29}{3}\)
\(=1-1\frac{14}{15}=\frac{14}{15}\)
Bài 3:
a) x/5 = 2/5
=> x =2
b) -4/x = 20/14 = 10/7
=> -4/x = 10/7
=> x.10 = (-4).7
x.10 = - 28
x= -28 :10
x= -2,8
c) 4/7 = 12/x = 12/ 21
=> 12/x = 12/21
=> x = 21
d) 3/7 = x / 21 = 9/21
=> x/21 = 9/21
=> x= 9
5 tháng 6 2018
\(\frac{5}{9}\) . \(\frac{a}{b}\) - \(\frac{11}{21}\) = \(\frac{4}{21}\)
\(\frac{5}{9}\) . \(\frac{a}{b}\) = \(\frac{4}{21}\) + \(\frac{11}{21}\)
\(\frac{5}{9}\) . \(\frac{a}{b}\) = \(\frac{5}{7}\)
\(\frac{a}{b}\) = \(\frac{5}{7}\) : \(\frac{5}{9}\)
\(\frac{a}{b}\) = \(\frac{9}{7}\)
Vậy \(\frac{a}{b}\) = \(\frac{9}{7}\)
HH
5 tháng 6 2018
5/9 x a/b-11/21=4/21
<=> 5/9 x a/b=4/21+11/21
<=> 5/9 x a/b = 21/21=1
<=> a/b = 1 : 5/9
<=> a/b=9/5
Vậy a/b=9/5
KN
1
AH
Akai Haruma
Giáo viên
29 tháng 1 2023
Lời giải:
a.
$x=\frac{7}{25}+\frac{-1}{5}=\frac{7}{25}+\frac{-5}{25}=\frac{7-5}{25}=\frac{2}{25}$
b.
$x=\frac{5}{11}+\frac{4}{-9}=\frac{5}{11}-\frac{4}{9}=\frac{45}{99}-\frac{44}{99}=\frac{1}{99}$
c.
$\frac{x}{-1}=\frac{-1}{3}-\frac{5}{9}=\frac{-3}{9}-\frac{5}{9}=\frac{-8}{9}$
$x=(-1).\frac{-8}{9}=\frac{8}{9}$
0
3
3 tháng 12 2019
\(a.=-2-\left(-5\right)-3+15-12\)
\(=3-3+15-12\)
\(=3\)
\(b.=-9-\left(-5\right)+\left(-21\right)-\left(-3\right)+\left(-11\right)-\left(-7\right)+\left(-4\right)\)
\(=-30\)
PT
1
CM
23 tháng 5 2017
a) 35
b) -53
c) 40 – - 7 2 = 40 – 49 = -9
d)| -15 + 21| - | 4 – 11 | = | 6 | - | -7 | = 6 – 7 = -1
OG
4
21 tháng 5 2021
a, = \(\frac{11}{21}\)x \(\left(\frac{7}{4}+\frac{5}{4}\right)\)
= \(\frac{11}{21}\)x 3
= \(\frac{33}{21}\)
b) = \(\left(\frac{23}{14}-\frac{9}{14}\right)\)x \(\frac{6}{13}\)
= 1 x \(\frac{6}{13}\)
= \(\frac{6}{13}\)
21 tháng 5 2021
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`5/9 xx a/b -11/21 =4/21`
`=> 5/9 xx a/b = 4/21 + 11/21`
`=> 5/9 xx a/b=15/21`
`=> a/b= 15/21 : 5/9`
`=>a/b= 15/21 xx 9/5`
`=> a/b=135/105`
`=>a/b=9/7`
Vậy `a/b=9/7`
\(\dfrac{5}{9}\times\dfrac{a}{b}-\dfrac{11}{21}=\dfrac{4}{21}\)
\(\Leftrightarrow\dfrac{5}{9}\times\dfrac{a}{b}=\dfrac{15}{21}\)
\(\Leftrightarrow\dfrac{a}{b}\times\dfrac{5}{9}=\dfrac{15}{21}\)
\(\Leftrightarrow\dfrac{a}{b}=\dfrac{15}{21}:\dfrac{5}{9}\)
\(\Leftrightarrow\dfrac{a}{b}=\dfrac{135}{105}=\dfrac{9}{7}\)
vaayjj : \(\dfrac{a}{b}=\dfrac{9}{7}\)