2,5 - (-6/9)
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9*9,8-2,5+9,8*9-9+2,5*8-2-6*2:3
=88,2-2,5+88,2-9+20-2-6*2:3
=88,2-2,5+88,2-9+20-2-4
=85,7+88,2-9+20-2-4
=173,9-9+20-2-4
=164,9+20-2-4
=184,9-2-4
=182,9-4
=178,9
Haiz phải là : 9 x 9,8 - 2,5 + 9,8 x 9 - 9 + 2,5 x 8 -2 - 6 x 2 : 3
= 9,8 x ( 9 + 9 + 9 - 9 ) - 2,5 x 8 - 2 - 6 x 2 : 3
= 9,8 x ( 9 + 9 + 9 - 9 ) - 2,5 x 8 - 2
= 9,8 x 18 - 2,5 x 8 - 2
= 176,4 - 20 - 2 = ( 176,4 - 20 ) -2 = 156,4 - 2 = 154,4 Thật ra là tự tính chứ không chắc ( "0 u 0")
\(6+2,5\times9\div\dfrac{4}{5}\times0,25\div0,1\)
`= 6+22,5`\(\div\)`4/5`\(\times\)`0,25`\(\div0,1\)
`= 6+28,125\(\times\)` `0,25`\(\div\)`0,1`
`=6+7,03125`\(\div0,1\)
`=6+70,3125`
`=76,3125`
\(\begin{array}{l}a)\frac{{ - 6}}{{18}} + \frac{{18}}{{27}}\\ = \frac{{ - 1}}{3} + \frac{2}{3}\\ = \frac{1}{3}\\b)2,5 - ( - \frac{6}{9})\\ = \frac{{25}}{{10}} + \frac{6}{9}\\ = \frac{5}{2} + \frac{2}{3}\\ = \frac{{15}}{6} + \frac{4}{6}\\ = \frac{{19}}{6}\\c) - 0,32.( - 0,875)\\ = \frac{{ - 32}}{{100}}.( - \frac{{875}}{{1000}})\\ = \frac{{ - 8}}{{25}}.(\frac{{ - 7}}{8})\\ = \frac{8}{{25}}.\frac{7}{8}\\ = \frac{7}{{25}}\\d)( - 5):2\frac{1}{5}\\ = ( - 5):\frac{{11}}{5}\\ = ( - 5).\frac{5}{{11}}\\ = \frac{{ - 25}}{{11}}\end{array}\)
a)\(\frac{7}{3}.\left( { - 2,5} \right).\frac{6}{7} = \frac{7}{3}.\frac{6}{7}.\left( { - 2,5} \right) = 2.\left( { - 2,5} \right) = - 5\)
b)
\(\begin{array}{l}0,8.\frac{{ - 2}}{9} - \frac{4}{5}.\frac{7}{9} - 0,2\\ = \frac{4}{5}.\frac{{ - 2}}{9} - \frac{4}{5}.\frac{7}{9}-\frac{2}{10}\\ = \frac{4}{5}.\left( {\frac{{ - 2}}{9} - \frac{7}{9}} \right) -\frac{1}{5}\\ = \frac{4}{5}.\left( { - 1} \right)-\frac{1}{5} \\= \frac{{ - 4}}{5}-\frac{1}{5}\\=\frac{-5}{5}\\=-1.\end{array}\)
1, Vì : \(\overline{2a3b}⋮2,5\Rightarrow b=0\)
Ta có : \(\overline{2a30}⋮9\)
\(\left(2+a+3+0\right)⋮9\)
\(\Rightarrow\left(5+a\right)⋮9\)
\(\Rightarrow9+\left(a-4\right)⋮9\)
Mà : \(9⋮9\Rightarrow a-4⋮9\)
=> a - 4 = 0
=> a = 0 + 4
=> a = 4
Vậy a = 4 ; b = 0
2, Ta có : \(\begin{cases}a-b=6\\11+a+6+b⋮9\end{cases}\) \(\Leftrightarrow\) \(\begin{cases}a-b=6\\17+a+b⋮9\end{cases}\)
a + b - 1 \(⋮\)9
Mà : \(0< a+b\le18\Rightarrow0< a+b-1\le17\)
\(\Rightarrow a+b-1=9\Rightarrow a+b=10\)
Mà : \(a-b=6\)
\(\Rightarrow\begin{cases}a=8\\b=2\end{cases}\)
Vậy a = 8 ; b = 2
`#3107.101107`
1.
`a,`
`2 - 2/3 + 2,5 + 1/3 + 3 + 1/2`
`= (2 + 2,5 + 3) - (2/3 - 1/3 - 1/2)`
`= 7,5 - (-1/6)`
`= 7,5 + 1/6`
`= 23/3`
`b,`
`9/10 - (6/5 * 3/2 + 7/4)`
`= 9/10 - (18/10 + 7/4)`
`= 9/10 - 18/10 - 7/4`
`= -9/10 - 7/4`
`= -53/20`
\(...=\dfrac{5}{2}+\dfrac{6}{9}=\dfrac{5}{2}+\dfrac{2}{3}=\dfrac{15}{6}+\dfrac{4}{6}=\dfrac{19}{6}\)