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\(=\dfrac{2^{19}\cdot3^9-3\cdot3^8\cdot2^{18}\cdot5}{2^{19}\cdot3^9+2^{20}\cdot3^{10}}=\dfrac{-3^{10}\cdot2^{18}}{2^{19}\cdot3^9\cdot7}=-\dfrac{3}{14}\)
\(\dfrac{a}{6}=\dfrac{b}{9}\)
\(\Leftrightarrow9a=6b\)
\(\Rightarrow3a=2b\)(chia cả 2 vế cho 3)
\(\Rightarrow3a-2b=0\Rightarrow\dfrac{3a-2b}{3a+2b}=0\)
Chúc bn học tốt
Ta có: `a/6 = b/9` `-> 9a = 6b`
`-> 3a = 2b`
Vì `3a = 2b` nên `3a - 2b = 0`.
`-> A = (3a - 2b)/(3a + 2b) = 0/(3a + 2b) = 0`
Vậy giá trị biểu thức `A` là `0`.
\(1,\\ a,2< 3\Rightarrow2^{30}< 3^{30}\Rightarrow-2^{30}>-3^{30}\\ b,6^{10}=6^{2\cdot5}=\left(6^2\right)^5=36^5>35^5\left(36>35\right)\)
\(2,\\ a,\dfrac{\left(-3\right)^{10}\cdot15^5}{25^3\cdot\left(-9\right)^7}=\dfrac{3^{10}\cdot5^5\cdot3^5}{5^6\cdot3^{14}}=\dfrac{3}{5}\\ b,\left(8x-1\right)^{2x+1}=5^{2x+1}\\ \Leftrightarrow8x-1=5\\ \Leftrightarrow x=\dfrac{3}{4}\)
Bài 2:
a: Ta có: \(\dfrac{\left(-3\right)^{10}\cdot15^5}{25^3\cdot\left(-9\right)^7}\)
\(=\dfrac{-3^{10}\cdot3^5\cdot5^5}{5^6\cdot3^{14}}\)
\(=-\dfrac{3}{5}\)
b: Ta có: \(\left(8x-1\right)^{2x+1}=5^{2x+1}\)
\(\Leftrightarrow8x-1=5\)
\(\Leftrightarrow8x=6\)
hay \(x=\dfrac{3}{4}\)
Ta có: \(B=\dfrac{30\cdot4^7\cdot3^{29}-5\cdot14^5\cdot2^{12}}{54\cdot6^{14}\cdot9^7-12\cdot8^5\cdot7^5}\)
\(=\dfrac{3^{30}\cdot2^{15}\cdot5-5\cdot2^{17}\cdot7^5}{3^{31}\cdot2^{15}-2^{17}\cdot3\cdot7^5}\)
\(=\dfrac{2^{15}\cdot5\left(3^{30}-2^2\cdot7^5\right)}{3\cdot2^{15}\left(3^{30}-2^2\cdot7^5\right)}\)
\(=\dfrac{5}{3}\)
\(A=\dfrac{4^5.9^4-2.6^9}{2^{10}.3^8+6^8.20}\)
\(=\dfrac{2^{10}.3^8-2.2^9.3^9}{2^{10}.3^8+2^8.3^8.2^2.5}\)
\(=\dfrac{2^{10}.3^8-2^{10}.3^9}{2^{10}.3^8+2^{10}.3^8.5}\)
\(=\dfrac{2^{10}.3^8\left(1-3\right)}{2^{10}.3^8\left(1+5\right)}\)
\(=-\dfrac{2}{6}=-\dfrac{1}{3}\)
\(A=\dfrac{2}{3}+\dfrac{-1}{3}=\dfrac{1}{3}\\ B=\dfrac{25}{11}\times\dfrac{13}{12}\times\dfrac{-11}{5}=\dfrac{5\times13\times\left(-1\right)}{1\times12\times1}=\dfrac{-65}{12}\\ C=\left(\dfrac{3}{4}-\dfrac{1}{5}\right)\times\left(\dfrac{2}{5}-\dfrac{4}{5}\right)=\dfrac{11}{20}\times\dfrac{-2}{5}=\dfrac{-11}{50}\)
\(B< -1< C< 0< A\\ \Leftrightarrow B< C< A\)
\(\dfrac{2^{50}.6^{10}.9^9}{12}=\dfrac{2^{50}.3^{10}.2^{10}.3^{27}}{12}=\dfrac{2^{60}.3^{37}}{3.2^2}=2^{48}.3^{36}\)