mình mới học lớp 3

a/ 7*25-49/7*24+21

=( 7*25 ) - ( 49/7 ) * ( 24+21)

= 175 - 7 * 45

= 175 - ( 7*45 )

=175 - 315

= -140

mk k bít đúng k

1: \(\dfrac{-7}{4}\cdot\dfrac{2}{9}=\dfrac{-14}{36}=\dfrac{-7}{18}\)

2: \(=\dfrac{12}{13}\cdot\dfrac{26}{5}=\dfrac{24}{5}\)

3: \(=\dfrac{20}{11}\cdot\dfrac{55}{21}=\dfrac{100}{21}\)

4: \(=\dfrac{-40}{240}=\dfrac{-1}{6}\)

a: \(\frac{3^{10}\cdot\left(-5\right)^{21}}{\left(-5\right)^{20}\cdot3^{12}}=\frac{-3^{10}\cdot5^{21}}{3^{12}\cdot5^{20}}=\frac{-5}{3^2}=-\frac59\)

b: \(\frac{-11^5\cdot13^7}{11^5\cdot13^8}=\frac{-11^5}{11^5}\cdot\frac{13^7}{13^8}=-\frac{1}{13}\)

c: \(2^{10}\cdot3^{10}-2^{10}\cdot3^9\)

\(=2^{10}\cdot3^9\cdot\left(3-1\right)\)

\(=2^{11}\cdot3^9\)

Ta có: \(\frac{2^{10}\cdot3^{10}-2^{10}\cdot3^9}{2^9\cdot3^{10}}\)

\(=\frac{2^{11}\cdot3^9}{2^{10}\cdot3^9}=2\)

d: \(5^{11}\cdot7^{12}+5^{11}\cdot7^{11}\)

\(=5^{11}\cdot7^{11}\left(7+1\right)=5^{11}\cdot7^{11}\cdot8\)

\(5^{12}\cdot7^{12}+9\cdot5^{11}\cdot7^{11}\)

\(=5^{11}\cdot7^{11}\left(5\cdot7+9\right)\)

\(=5^{11}\cdot7^{11}\left(35+9\right)=5^{11}\cdot7^{11}\cdot44\)

Ta có: \(\frac{5^{11}\cdot7^{12}+5^{11}\cdot7^{11}}{5^{12}\cdot7^{12}+9\cdot5^{11}\cdot7^{11}}\)

\(=\frac{5^{11}\cdot7^{11}\cdot8}{5^{11}\cdot7^{11}\cdot44}=\frac{8}{44}=\frac{2}{11}\)

=\(\dfrac{1.\left(-1\right).\left(-3\right).\left(-2\right)}{1.2.1.2}\)

\(=\dfrac{-6}{4}\)

\(=-\dfrac{3}{4}\)

a, \(\frac{7.25-49}{7.24+21}=\frac{7.25-7.7}{7.24+7.3}=\frac{7.\left(25-7\right)}{7.\left(24+3\right)}=\frac{7.18}{7.27}=\frac{7.9.2}{7.9.3}=\frac{2}{3}\)

b, \(\frac{2.\left(-13\right).9.10}{-3.4.\left(-5\right).26}=\frac{2.13.\left(-3\right).3.\left(-2\right).\left(-5\right)}{-3.\left(-2\right).\left(-2\right).\left(-5\right).2.13}=\frac{-3}{2}\)

a)\(\frac{2}{3}\)

b)\(-\frac{3}{2}\)

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