Tìm x:
X + 7 = 89 X + 8 = 69
X + 6 = 34 X + 9 = 23
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\(X:\dfrac{3}{9}=\dfrac{7}{8}\)
\(X=\dfrac{7}{8}\times\dfrac{3}{9}\)
\(X=\dfrac{21}{72}\)
\(\left(X-21\times13\right):11=30\)
\(X-273=330\)
\(X=603\)
`x:3/9=7/8`
`x=7/8xx3/9`
`x=7/24`
`-------------`
`(x-21xx13):11=30`
`(x-273):11=30`
`x-273=30xx11`
`x-273=330`
`x=330-273`
`x=57`
a: \(=\dfrac{17}{7}+\dfrac{2}{9}-\dfrac{10}{7}-\dfrac{5}{3}\cdot9=1+\dfrac{2}{9}-15=-14+\dfrac{2}{9}=-\dfrac{126}{9}+\dfrac{2}{9}=-\dfrac{124}{9}\)
b: \(=\dfrac{-11}{23}\left(\dfrac{6}{7}+\dfrac{8}{7}\right)-\dfrac{1}{23}=\dfrac{-22}{23}-\dfrac{1}{23}=-1\)
c: \(=\left(\dfrac{377}{-231}-\dfrac{123}{89}+\dfrac{34}{791}\right)\cdot\dfrac{4-3-1}{24}=0\)
d: \(=\dfrac{12}{7}\left(19+\dfrac{5}{8}-15-\dfrac{1}{4}\right)=\dfrac{12}{7}\cdot\dfrac{35}{8}=\dfrac{15}{2}\)
a) 1 - 2 + 3 - 4 + 5 - 6 + 7 - 8 + 9 - 10 + 11
= (1 - 2) + (3 - 4) + (5 - 6) + (7 - 8) + (9 - 10) + 11
= -1 + (-1) + (-1) + (-1) + (-1) + 11
= -1 x 5 + 11
= -5 + 11
= 6
b) 98 + 87 + 76 + ... + 21 - 12 - 23 - 34 - ... - 89
= (98 89) + (87 - 78) + ... + (21 - 12) (có 8 nhóm)
= 9 + 9 + ... + 9 (có 8 số 9)
= 9 x 8
= 72
\(1-2+3-4+.....-10+11\)
\(=\left(1-2\right)+\left(3-4\right)+...\left(9-10\right)+11\)
\(=1+\left(-1\right)+\left(-1\right)+\left(-1\right)+\left(-1\right)+11\)
\(=-1\times5+11\)
\(=6\)
a: \(=\dfrac{-3}{7}+\dfrac{15}{26}-\dfrac{2}{13}+\dfrac{3}{7}=\dfrac{15}{26}-\dfrac{4}{26}=\dfrac{11}{26}\)
b: \(=\dfrac{6}{7}+\dfrac{2}{9}-\dfrac{10}{7}-5=\dfrac{-4}{7}-5+\dfrac{2}{9}=-\dfrac{337}{63}\)
c: \(=-\dfrac{11}{23}\left(\dfrac{6}{7}+\dfrac{8}{7}\right)-\dfrac{1}{23}=\dfrac{-22}{23}-\dfrac{1}{23}=-1\)
\(x=\dfrac{4}{5}\times\dfrac{4}{3}\)
\(x=\dfrac{16}{15}\)
-----------------------
\(x=\dfrac{5}{9}\times\dfrac{3}{8}\)
\(x=\dfrac{5}{24}\)
1)
\(2.\frac{3}{7}+\left(\frac{2}{9}-1\frac{3}{7}\right)-\frac{5}{3}:\frac{1}{9}\)
\(=\frac{6}{7}+\frac{2}{9}-\frac{10}{7}-\frac{5}{3}.9\)
\(=\left(\frac{6}{7}-\frac{10}{7}\right)+\frac{2}{9}-15\)
\(=\frac{-4}{7}+\frac{2}{9}-\frac{15}{1}\)
\(=\frac{-36}{63}+\frac{14}{63}-\frac{945}{63}\)
\(=\frac{-967}{63}\)
2)
\(-\frac{11}{23}.\frac{6}{7}+\frac{8}{7}.\frac{-11}{23}-\frac{1}{23}\)
\(=\frac{-11}{23}\left(\frac{6}{7}+\frac{8}{7}\right)-\frac{1}{23}\)
\(=\frac{-11}{23}.2-\frac{1}{23}\)
\(=\frac{-22}{23}-\frac{1}{23}\)
\(=\frac{-23}{23}\)
\(=-1\)
3)
\(\left(\frac{377}{-231}-\frac{123}{89}+\frac{34}{791}\right).\left(\frac{1}{6}-\frac{1}{8}-\frac{1}{24}\right)\)
\(=\left(\frac{377}{-231}-\frac{123}{89}+\frac{34}{791}\right).\left(\frac{4}{24}-\frac{3}{24}-\frac{1}{24}\right)\)
\(=\left(\frac{377}{-231}-\frac{123}{89}+\frac{34}{791}\right).\frac{0}{24}\)
\(=\left(\frac{377}{-231}-\frac{123}{89}+\frac{34}{791}\right).0\)
\(=0\)
x + 7 = 89
x = 89 - 7
x = 82
x + 6 = 34
x = 34 - 6
x = 28
x + 8 = 89
x = 89 - 8
x = 81
x + 9 = 23
x = 23 - 9
x = 14
+) x+7=89
x= 89-7=82
vậy x=82
+) x+8=69
x=69-8=61
vậy x=61
+) x+6=34
x= 34-6=28
vậy x= 38
+ x+9=23
x= 23-9=14
vậy x=14