tính bằng cách hợp lý:5/8x4+5/8x4/5 giúp tui câu này nha
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C1:
`5/8 xx (1/5 +2)`
`=5/8 xx (1/5 +10/5)`
`=5/8 xx 11/5`
`=11/8`
C2:
`5/8 xx (1/5 +2)`
`=5/8 xx 1/5 + 5/8 xx 2`
`=1/8 + 10/8`
`=11/8`
\(\dfrac{1}{1.4}+\dfrac{1}{4.2}+\dfrac{1}{2.8}+\dfrac{1}{8.4}+\dfrac{1}{4.16}+\dfrac{1}{16.8}\)
= \(\dfrac{1}{4}.\left(1+\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}+\dfrac{1}{32}\right)\)
= \(\dfrac{1}{4}.\left(\dfrac{3}{2}+\dfrac{3}{8}+\dfrac{3}{32}\right)\)
= \(\dfrac{1}{4}.\dfrac{3}{2}\left(1+\dfrac{1}{4}+\dfrac{1}{16}\right)\)
= \(\dfrac{1}{4}.\dfrac{3}{2}\left(\dfrac{16}{16}+\dfrac{4}{16}+\dfrac{1}{16}\right)\)
= \(\dfrac{3}{8}.\dfrac{21}{16}\)
= \(\dfrac{63}{128}\)
\(\frac{1}{8}.\frac{4}{5}-1=\frac{1}{10}-1=\frac{-9}{10}\)
Dễ :v
Câu 1:
A={1;3;5;7;9}
Câu 2:
A. 24 x 82 + 24 x 18 - 100
= 24 x (82 + 18) - 100
= 24 x 100 - 100
= 2400 - 100 = 2300
B.12 + 3 [ 39 - (5 - 2 )2 ]
= 12 + 3. [39 - 32 ]
= 12 + 3 . [39-9]
= 12 + 3.30
= 12 + 90 = 102
\(3x+2x=\frac{5}{8}.\frac{4}{3}\)
\(\Rightarrow5x=\frac{5}{6}\)
\(\Rightarrow x=\frac{5}{6}:5\)
\(\Rightarrow x=\frac{1}{6}\)
Vậy x = \(\frac{1}{6}\)
\(3x+2x=\frac{5}{8}.\frac{4}{3}\)
\(5x=\frac{5}{6}\)
\(x=\frac{5}{6}:5\)
\(x=\frac{1}{6}\)
a) = 4x ( 12 + 1 ) +5
= 4 x 13 + 5
= 57
b)= (8x4 + 8x6) +8x 5
= 8x 10 + 8x5
= 80 + 40
= 120
c) = 2 + 3x2 + 4x2 + 3x2
= 2 + ( 2 x 10 )
= 2 + 20
= 22
\(\frac{7}{9}+\frac{6}{7}\times\frac{4}{5}=\frac{7}{9}+\frac{24}{35}=\frac{361}{315}\)
\(\frac{21}{23}+\frac{4}{5}:\frac{6}{8}=\frac{21}{23}+\frac{16}{15}=\frac{548}{345}\)
\(\frac{5}{8}\times\frac{4}{9}:\frac{2}{3}=\frac{5}{18}:\frac{2}{3}=\frac{5}{12}\)
\(\frac{7}{12}+\frac{5}{6}-\frac{21}{24}=\frac{14}{24}+\frac{20}{24}-\frac{21}{24}=\frac{11}{24}\)
b,
\(\frac{21}{23}+\frac{4}{5}:\frac{6}{8}=\frac{21}{23}+\frac{4}{5}.\frac{8}{6}=\frac{21}{23}+\frac{16}{15}=1\frac{338}{345}\)
c,
\(\frac{5}{8}.\frac{4}{9}.\frac{3}{2}=\frac{5}{12}\)
d,
\(\frac{7}{12}+\frac{5}{6}-\frac{21}{24}=\frac{14}{24}+\frac{20}{24}-\frac{21}{24}=\frac{13}{24}\)
chán thật
\(\dfrac{5}{8}\) x 4 + \(\dfrac{5}{8}\) x \(\dfrac{4}{5}\)
= \(\dfrac{5}{8}\) x (\(4\) + \(\dfrac{4}{5}\) )
= \(\dfrac{5}{8}\) x \(\dfrac{24}{5}\) = 3
\(\dfrac{5}{8}\times4+\dfrac{5}{8}\times\dfrac{4}{5}\)
\(=\dfrac{5}{8}\times\left(4+\dfrac{4}{5}\right)\)
\(=\dfrac{5}{8}\times\dfrac{24}{5}\)
\(=\dfrac{24}{8}\)
\(=3\)