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A = (3,1 – 2,5) – (-2,5 + 3,1) = 3,1 – 2,5 + 2,5 – 3,1 = 0
B = (5,3 – 2,8) – (4 + 5,3) = 5,3 – 2,8 – 4 – 5,3
A=(3,1-2,5)-(-2,5+3,1)=3,1-2,5+2,5-3,1=0
B=(5,3-2,8)-(4+5,3)=5,3-2,8-4-5,3=-6,8
d.\(x:4\dfrac{1}{2}=-2,5\)
\(x:\dfrac{9}{2}=-\dfrac{5}{2}\)
\(x=-\dfrac{5}{2}\times\dfrac{9}{2}\)
\(x=-\dfrac{45}{4}\)
e.\(\left(\dfrac{x}{7}+1\right):\left(-4\right)=-\dfrac{1}{28}\)
\(\dfrac{x}{7}+1=\dfrac{1}{7}\)
\(\dfrac{x}{7}=-\dfrac{6}{7}\)
\(x=-6\)
\(\frac{19}{4}-\frac{37}{100}+\frac{1}{8}-\frac{32}{25}-\frac{5}{2}+\frac{7}{2}=\left(\frac{19}{4}-\frac{37}{100}-\frac{32}{25}\right)+\left(\frac{7}{2}-\frac{5}{2}\right)+\frac{1}{8}=\frac{31}{10}+1+\frac{1}{8}=\frac{169}{40}\)
\(=\frac{19}{4}+\left(-\frac{37}{100}\right)+\left(-\frac{32}{25}\right)+\left(-\frac{5}{2}\right)+\frac{7}{2}\)
\(=\frac{219}{50}+\left(-\frac{32}{25}\right)+\left(-\frac{5}{2}\right)+\frac{7}{2}\)
\(=\frac{31}{10}+\left(-\frac{5}{2}\right)+\frac{7}{2}\)
\(=\frac{31}{10}+\left(-\frac{25}{10}\right)+\frac{35}{10}\)
\(=\frac{41}{10}\)
\(4\frac{3}{4}+\left(-0,37\right)+\left(-1,28\right)+\left(-2,5\right)+3\frac{1}{2}\)
\(=\frac{19}{4}-\frac{37}{100}-\frac{128}{100}-\frac{25}{10}+\frac{7}{2}\)
\(=\frac{475}{100}-\frac{37}{100}-\frac{128}{100}-\frac{250}{100}+\frac{350}{100}\)
\(=\frac{410}{100}=4,1\)
1,
\(\begin{array}{l}2,5.\left( {4,1 - 3 - 2,5 + 2.7,2} \right) + 4,2:2\\ = 2,5.\left( {4,1 - 3 - 2,5 + 14,4} \right) + 4,2:2\\ = 2,5.\left( {1,1 - 2,5 + 14,4} \right) + 2,1\\ = 2,5.\left( { - 1,4 + 14,4} \right) + 2,1\\ = 2,5.13 + 2,1\\ = 32,5 + 2,1\\ = 34,6\end{array}\)
2,
Cách 1:
\(\begin{array}{l}2,86.4 + 3,14.4 - 6,01.5 + {3^2}\\ = 11,44 + 12,56 - 30,05 + 9\\ = \left( {11,44 + 12,56} \right) + \left( { - 30,05 + 9} \right)\\ = 24 + \left( { - 21,05} \right)\\ = 24 - 21,05\\ = 2,95\end{array}\)
Cách 2:
\(\begin{array}{l}2,86.4 + 3,14.4 - 6,01.5 + {3^2}\\ = 4.(2,86+3,14) - 30,05 + 9\\ = 4.6 + \left( { - 30,05 + 9} \right)\\ = 24 + \left( { - 21,05} \right)\\ = 24 - 21,05\\ = 2,95\end{array}\)
\(\left|x-1,5\right|+\left|2,5+x\right|=0\)
\(\Rightarrow\left|x-1,5\right|\ge0\)
\(\Rightarrow\left|2,5-x\right|\ge0\)
Nên : + ) \(x-1,5=0\)
\(\Leftrightarrow x=1,5\)
+ ) \(2,5-x=0\)
\(\Leftrightarrow x=2,5\)
Ta có : \(1,5+2,5\ne0\)
Vậy x vô nghiệm .
= 1.6,25+(-15,625):6,25
= 6,25+(-2,5)
= 3,75