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\(\frac{3^{10}.\left(-5\right)^{21}}{\left(-5\right)^{20}.3^{12}}=\frac{3^{10}.\left(-5\right)^{20}.\left(-5\right)}{\left(-5\right)^{20}.3^{10}.3^2}=\frac{-5}{3^2}=-\frac{5}{9}\)
Ta có:\(\frac{3^{10}\cdot\left(-5\right)\cdot21}{\left(-5\right)^{20}\cdot3^{12}}\)
\(=\frac{3^{10}\cdot\left(-5\right)\cdot21}{\left(-5\right)^{19}\cdot\left(-5\right)\cdot3^{12}}\)
\(=\frac{3\cdot7}{\left(-5\right)^{19}\cdot3^2}\)
\(=\frac{7}{\left(-5\right)^{19}\cdot3}\)
\(\frac{\left(-11\right)^5.13^7}{11^5.13^8}=\frac{\left(-11\right)^5.13^7}{11^5.13^7}.\frac{1}{13}=-1.\frac{1}{13}=-\frac{1}{13}\)
\(\frac{3^{10}.\left(-5\right)^{21}}{\left(-5\right)^{20}.3^{12}}=\frac{3^{10}.\left(-5\right)^{20}.\left(-5\right)}{\left(-5\right)^{20}.3^{10}.3^2}=\frac{-5}{3^2}=\frac{-5}{9}\)
2.\(B=\frac{1}{2}.\frac{2}{3}.\frac{3}{4}.......\frac{49}{50}=\frac{1}{50}\)
\(=\frac{3^{10}.\left(-5\right)^{20}.\left(-5\right)^1}{\left(-5\right)^{20}.3^{10}.3^2}\)\(=\frac{\left(-5\right)^1}{3^2}\)\(=\frac{-5}{9}\)
Hok tốt !
\(\frac{3^{10}.\left(-5\right)^{20}.\left(-5\right)^1}{\left(-5\right)^{20}.3^{10}.3^2}=\frac{-5}{3^2}=\frac{-5}{9}\)
\(\frac{3^{10}.\left(-5\right)^{21}}{\left(-5\right)^{20}.3^{12}}=\frac{1.\left(-5\right)}{1.3^2}=-\frac{5}{9}\)
Chúc bạn học tốt
Giari thích :
\(3^{12}:3^{10}=3^{12-10}=3^2=9\)
\(\left(-5\right)^{21}:\left(-5\right)^{20}=\left(-5\right)^{21-20}=\left(-5\right)^1=\left(-5\right)\)
\(\frac{3^{10}.\left(-5\right)^{21}}{\left(-5\right)^{20}.3^{12}}\)
\(=\frac{\left(-5\right)}{3^2}\)
\(=\frac{-5}{9}\)
OK