Question

1.Tính hợp lí

a) \(0,7+\dfrac{-7}{19}-\left(-0,3\right)\)

b) \(\dfrac{5}{3}.\left(-2,5\right):\dfrac{5}{6}\)

c) \(0,6.\dfrac{-5}{17}-\dfrac{3}{5}.\dfrac{12}{17}\)

d) \(\dfrac{7}{4}.\dfrac{5}{2}-\dfrac{7}{4}.\dfrac{3}{2}\)

Giúp tui với!

Answer 1

1. Tính hợp lí

a) \(0,7+\dfrac{-7}{19}-\left(-0,3\right)\)

\(=\dfrac{7}{10}+\dfrac{-7}{19}+\dfrac{3}{10}\)

\(=\left(\dfrac{7}{10}+\dfrac{3}{10}\right)+\dfrac{-7}{19}\)

\(=1+\dfrac{-7}{19}\)

\(=\dfrac{12}{19}\)

b) \(\dfrac{5}{3}.\left(-2,5\right):\dfrac{5}{6}\)

\(=\dfrac{5}{3}.\dfrac{-5}{2}.\dfrac{6}{5}\)

\(=\left(\dfrac{5}{3}.\dfrac{6}{5}\right).\dfrac{-5}{2}\)

\(=2.\dfrac{-5}{2}\)

\(=-5\)

c) \(0,6.\dfrac{-5}{17}-\dfrac{3}{5}.\dfrac{12}{17}\)

\(=\dfrac{3}{5}.\dfrac{-5}{17}-\dfrac{3}{5}.\dfrac{12}{17}\)

\(=\dfrac{3}{5}.\left(\dfrac{-5}{17}-\dfrac{12}{17}\right)\)

\(=\dfrac{3}{5}.-1\)

\(=\dfrac{-3}{5}\)

d) \(\dfrac{7}{4}.\dfrac{5}{2}-\dfrac{7}{4}.\dfrac{3}{2}\)

\(=\dfrac{7}{4}.\left(\dfrac{5}{2}-\dfrac{3}{2}\right)\)

\(=\dfrac{7}{4}.1\)

\(=\dfrac{7}{4}\)

Chúc bạn học tốt

Answer 2

a) 0,7+−719−(−0,3)0,7+19−7​−(−0,3)

=710+−719+310=107​+19−7​+103​

=(710+310)+−719=(107​+103​)+19−7​

=1+−719=1+19−7​

=1219=1912​

b) 53.(−2,5):5635​.(−2,5):65​

=53.−52.65=35​.2−5​.56​

=(53.65).−52=(35​.56​).2−5​

=2.−52=2.2−5​

$=-5$

c) 0,6.−517−35.12170,6.17−5​−53​.1712​

=35.−517−35.1217=53​.17−5​−53​.1712​

=35.(−517−1217)=53​.(17−5​−1712​)

=35.−1=53​.−1

=−35=5−3​

d) 74.52−74.3247​.25​−47​.23​

=74.(52−32)=47​.(25​−23​)

=74.1=47​.1

=74=47​

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