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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
a; \(\dfrac{9}{27}\) + \(\dfrac{7}{-49}\)
= \(\dfrac{1}{3}\) - \(\dfrac{1}{7}\)
= \(\dfrac{7}{21}\) - \(\dfrac{3}{21}\)
= \(\dfrac{4}{21}\)
b; - \(\dfrac{12}{10}\) + \(\dfrac{-25}{30}\)
= - \(\dfrac{6}{5}\) - \(\dfrac{5}{6}\)
= -\(\dfrac{36}{30}\) - \(\dfrac{25}{30}\)
= \(\dfrac{-61}{30}\)
c; \(\dfrac{-20}{35}\) + \(\dfrac{-16}{-24}\)
= - \(\dfrac{4}{7}\) + \(\dfrac{2}{3}\)
= - \(\dfrac{12}{21}\) + \(\dfrac{14}{21}\)
= \(\dfrac{2}{21}\)
d; - \(\dfrac{21}{77}\) + \(\dfrac{10}{-35}\)
= - \(\dfrac{3}{11}\) - \(\dfrac{2}{7}\)
= - \(\dfrac{21}{77}\) - \(\dfrac{22}{77}\)
= - \(\dfrac{43}{77}\)
Bài giải
Ta có: \(\frac{49+\left(-49\right).\left(-2\right)}{7.21}\)
= \(\frac{49.1+49.2}{7.21}\)
= \(\frac{49.\left(1+2\right)}{7.21}\)
= \(\frac{49.3}{7.21}\)
= \(\frac{7.7.3}{7.7.3}\)
= \(1\)
\(\frac{7\cdot25-49}{7\cdot24+21}=\frac{7\cdot25-7\cdot7}{7\cdot24+7\cdot3}\)
\(=\frac{7\cdot\left(25-7\right)}{7\left(24+3\right)}\)
\(=\frac{7\cdot18}{7\cdot27}=\frac{2}{3}\)
\(@Cothanhkhe\)
3 x 8/15 x 12 = 3x8/15 x12 = 24/15 x 12 = 288/15
7 x 25-49/7 x 24+21= 175 - 7 x24 + 21 =4053
2 x (-13) x 9 x 10/(-3) x 4 x (-5) x 26= -26 x 9 x 10 / 1560 = -234 x 1/156 = -3/2
\(\dfrac{\left(-6\right).11}{\left(-11\right).\left(-8\right)}=\dfrac{\left(-3\right).2.11}{11.2.4}=-\dfrac{3}{4}\)
\(\dfrac{21.\left(-5\right)}{25.\left(-7\right)}=\dfrac{\left(-3\right).\left(-7\right).\left(-5\right)}{\left(-5\right).\left(-5\right).\left(-7\right)}=\dfrac{3}{5}\)
\(\dfrac{32.9.11}{12.24.22}=\dfrac{4.4.2.3.3.11}{3.4.4.2.3.11.2}=\dfrac{4^2.2.3^2.11}{3^2.4^2.2^2.11}=\dfrac{1}{2}\)
\(\dfrac{\left(-6\right).11}{\left(-11\right).\left(-8\right)}\)=\(\dfrac{-3}{4}\)
\(\dfrac{21.\left(-5\right)}{25.\left(-7\right)}\)=\(\dfrac{2}{5}\)
\(\dfrac{32.9.11}{12.24.22}\)=\(\dfrac{1}{2}\)
\(\frac{3\times21}{14\times15}=\frac{1\times21}{14\times5}=\frac{21}{70}=\frac{3}{10}\)
\(\frac{49+7\times49}{49}=\frac{392}{49}=8\)