Tính)
a) 5+3x52/-8
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A=5/8.(-3/7-4/7)+16125/8
= 5/8.(-1)+16125/8
=-5/8+16125/8
=16120/8=2015
k nha
a) 7/15 + 4/5 = 7/15 + 12/15 = 19/15
b) 4/5 x 5/8= 1/2
c) 2/3 - 3/8= 16/24 - 9/24 = 7/24
d) 1/2 : 2/5= 1/2 x 5/2= 5/4
a) \(\dfrac{7}{15}+\dfrac{4}{5}=\dfrac{7}{15}+\dfrac{12}{15}=\dfrac{19}{15}\)
b) \(\dfrac{4}{5}\times\dfrac{5}{8}=\dfrac{20}{40}=\dfrac{1}{2}\)
c) \(\dfrac{2}{3}-\dfrac{3}{8}=\dfrac{16}{24}-\dfrac{9}{24}=\dfrac{7}{24}\)
d) \(\dfrac{1}{2}:\dfrac{2}{5}=\dfrac{1}{2}\times\dfrac{5}{2}=\dfrac{5}{4}\)
a: \(=\left(\dfrac{5}{8}-\dfrac{28}{8}\right)\cdot\dfrac{5}{6}=\dfrac{-23}{8}\cdot\dfrac{5}{6}=\dfrac{-115}{48}\)
b: \(=\dfrac{4}{7}\cdot\dfrac{24+25}{15}=\dfrac{4}{7}\cdot\dfrac{49}{15}=\dfrac{28}{15}\)
c: \(=\dfrac{7}{2}:\dfrac{24-10}{15}=\dfrac{7}{2}\cdot\dfrac{15}{14}=\dfrac{15}{4}\)
\(a,\dfrac{4}{5}+\dfrac{2}{7}=\dfrac{28}{35}+\dfrac{10}{35}=\dfrac{38}{35}.\)
\(b,2-\dfrac{8}{9}=\dfrac{18}{9}-\dfrac{8}{9}=\dfrac{10}{9}.\)
\(c,\dfrac{5}{8}\times3=\dfrac{5\times3}{8}=\dfrac{15}{8}.\)
\(d,5:\dfrac{6}{21}=5\times\dfrac{21}{6}=\dfrac{5\times21}{6}=\dfrac{105}{6}=\dfrac{35}{2}.\)
\(đ,\dfrac{3}{5}\times\dfrac{4}{5}\times\dfrac{6}{7}=\dfrac{3\times4\times6}{5\times5\times7}=\dfrac{72}{175}.\)
\(a,\dfrac{4}{5}+\dfrac{2}{7}=\dfrac{28}{35}+\dfrac{10}{35}=\dfrac{38}{35}\)
\(b,2-\dfrac{8}{9}=\dfrac{18}{9}-\dfrac{8}{9}=\dfrac{10}{9}\)
\(c,\dfrac{5}{8}\times3=\dfrac{5\times3}{8\times1}=\dfrac{15}{8}\)
\(d,\dfrac{3}{5}\times\dfrac{4}{5}\times\dfrac{6}{7}=\dfrac{3\times4\times6}{5\times5\times7}=\dfrac{72}{175}\)
\(5+3\times5^2\div(-8)\)
\(=5+3\times25\div\left(-8\right)\)
\(=5+\frac{-75}{8}\)
\(=\frac{-35}{8}\)
\(5+3.5^2:\left(-8\right)\)
\(=5+3.25:\left(-8\right)\)
\(=5+\left(-\frac{75}{8}\right)\)
\(=-\frac{35}{8}\)