rút gọn :
3^10.-5^21
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\(\frac{3^{10}.\left(-5\right)^{21}}{\left(-5\right)^{20}.3^{12}}\)= \(\frac{3^{10}.\left(-5\right)^{20}.\left(-5\right)}{\left(-5\right)^{20}.3^{10}.3^2}\)= \(\frac{\left(-5\right)}{3^2}\)= \(\frac{-5}{9}\)
\(\frac{3^{10}.\left(-5\right)^{21}}{\left(-5\right)^{20}.3^{12}}=\frac{3^{10}.\left(-5\right)^{20}.\left(-5\right)}{\left(-5\right)^{20}.3^{10}.3^2}=\frac{-5}{3^2}\)
CHÚC BẠN HỌC TỐT!!!!
\(\dfrac{7}{30}=\dfrac{21}{90};\dfrac{4}{45}=\dfrac{8}{90}\)
\(\frac{2.5^{22}-9.5^{21}}{25^{10}}=\frac{2.5^2.5^{20}-9.5.5^{20}}{\left[\left(5\right)^2\right]^{10}}=\frac{5^{20}\left(2.5^2-9.5\right)}{5^{20}}=2.5^2-9.5=5\left(10-9\right)=5.1=5\)
\(\frac{2\cdot5^{22}-9\cdot5^{21}}{25^{10}}=\frac{\left(2\cdot5-9\right)\cdot5^{21}}{25^{10}}=\frac{5^{21}}{5^{20}}=5\)
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
Ta có:\(\frac{3^{10}\cdot\left(-5\right)\cdot21}{\left(-5\right)^{20}\cdot3^{12}}\)
\(=\frac{3^{10}\cdot\left(-5\right)\cdot21}{\left(-5\right)^{19}\cdot\left(-5\right)\cdot3^{12}}\)
\(=\frac{3\cdot7}{\left(-5\right)^{19}\cdot3^2}\)
\(=\frac{7}{\left(-5\right)^{19}\cdot3}\)
a: \(\dfrac{3}{9}\times\dfrac{5}{4}=\dfrac{5}{4}\times\dfrac{1}{3}=\dfrac{5\times1}{4\times3}=\dfrac{5}{12}\)
b: \(\dfrac{10}{15}\times\dfrac{3}{5}=\dfrac{3}{5}\times\dfrac{2}{3}=\dfrac{3\times2}{5\times3}=\dfrac{2}{5}\)
c: \(\dfrac{5}{8}\times\dfrac{4}{12}=\dfrac{5}{8}\times\dfrac{1}{3}=\dfrac{5}{3\times8}=\dfrac{5}{24}\)
d: \(\dfrac{9}{27}\times\dfrac{3}{21}=\dfrac{1}{7}\times\dfrac{1}{3}=\dfrac{1\times1}{7\times3}=\dfrac{1}{21}\)