12.5 . -5/7 + 9 3/4 - 1.5 . 5/7
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12,5 : (-7,5) + 1,5 : (-7,5)
= 12,5 . (-5/7) + 1,5 . (-5/7)
= (12,5 + 1,5) . (-5/7)
= 14 . (-5/7)
= -10
\(=\dfrac{5}{7}\cdot\dfrac{3}{11}-\dfrac{5}{7}\cdot\dfrac{9}{11}+\dfrac{5}{7}=\dfrac{5}{7}\left(\dfrac{3}{11}-\dfrac{9}{11}+1\right)=\dfrac{5}{7}\cdot\dfrac{5}{11}=\dfrac{25}{77}\)
\(\dfrac{5}{7} . \dfrac{3}{11} + \dfrac{-5}{7} . \dfrac{9}{11} + 1 . \dfrac{5}{7} \)
\(= \dfrac{5}{7} . \dfrac{3}{11} - \dfrac{5}{7} . \dfrac{9}{11} + 1 .\dfrac{5}{7} \)
\(= \dfrac{5}{7} . ( \dfrac{3}{11} - \dfrac{9}{11} - 1 )\)
\(= \dfrac{5}{7} . \dfrac{5}{11} \)
\(= \dfrac{25}{77} \)
a: =6-6=0
b: \(=\dfrac{-5}{4}:\dfrac{2-7}{8}+\dfrac{3}{2}\cdot\dfrac{2-5}{6}\)
\(=\dfrac{-5}{4}\cdot\dfrac{8}{-5}+\dfrac{3}{2}\cdot\dfrac{-3}{6}\)
\(=2+\dfrac{-9}{12}=2-\dfrac{3}{4}=\dfrac{5}{4}\)
c: \(=2,5\cdot\left(-0,65\right)+1,5\left(-0,3-0,35\right)=-0,65\cdot4=-2,6\)
12.5 . -5/7 + 9 3/4 - 1.5 . 5/7
\(=\frac{5}{7}.\left(-60\right)+\frac{39}{4}-5.\frac{5}{7}\)
\(=\frac{5}{7}.\left[\left(-60\right)-5\right]+\frac{39}{4}\)
\(=\frac{5}{7}.\left(-65\right)+\frac{39}{4}\)
\(=\frac{-325}{7}+\frac{39}{4}=\frac{-1027}{28}\)
học tốt
= 25/2 . -5/7+ 39/4 + -3/2 . 5/7 = -125/14 + 39/4 + -15/14 = ( -125/14 + -15/14 ) + 39/4 = -10 + 39/4 = -1/4