Rút gọn phân số 9 14 .25 5 .8 7 18 12 .625 3 .24 3 ta được
A. 9 5
B. 9 25
C. 3 25
D. 3 5
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\(\frac{9^{14}.25^5.8^7}{18^{12}.625^3.24^3}=\frac{\left(3^2\right)^{14}.\left(5^2\right)^5.\left(2^3\right)^7}{\left(2.3^2\right)^{12}.\left(5^4\right)^3.\left(3.2^3\right)^3}=\frac{3^{28}.5^{10}.2^{21}}{2^{12}.3^{24}.5^{12}.3^3.2^9}=\frac{3^{28}.5^{10}.2^{21}}{2^{21}.3^{27}.5^{12}}=\frac{3}{5^2}=\frac{3}{25}\)
\(\frac{374}{506}=\frac{2.187}{253.2}=\frac{187}{253}\)
\(\frac{9^{14}.25^5.8^7}{18^{12}.625^3.24^3}\)
\(=\frac{3^{28}.5^{10}.2^{21}}{2^{12}.9^{12}.5^{12}.3^3.8^3}\)
\(=\frac{3^{28}.5^{10}.2^{21}}{2^{12}.3^{24}.5^{12}.3^3.2^9}\)
\(=\frac{3^{28}.5^{10}.2^{21}}{2^{21}.3^{27}.5^{12}}\)
\(=\frac{3}{5^2}\)
\(\dfrac{9^{14}\cdot25^5\cdot8^7}{18^2\cdot625^3\cdot24^3}\)
\(=\dfrac{3^{42}\cdot5^{10}\cdot2^{21}}{2^2\cdot3^4\cdot5^{12}\cdot2^9\cdot3^3}=\dfrac{3^{42}\cdot5^{10}\cdot2^{21}}{2^{11}\cdot3^7\cdot5^{12}}\)
\(=\dfrac{3^{35}}{5^2}\cdot2^{10}\)
\(\frac{9^{14}.25^5.8^2.8^7}{18^{12}.625^3.24^3}=\frac{3^{28}.5^{10}.8^9}{2^{12}.9^{12}.5^{12}.3^3.2^9}\)\(=\frac{3^{28}.5^{10}.2^{27}}{2^{21}.5^{12}.3^{24}.3^3}=\frac{3^{28}.5^{10}.2^{27}}{2^{21}.5^{12}.3^{27}}\) \(=\frac{3.2^6}{5^2}=\frac{192}{25}=7,68\)
Đáp án cần chọn là: C
9 14 .25 5 .8 7 18 12 .625 3 .24 3 = 3 2 14 . 5 2 5 . 2 3 7 2.3 2 12 . 5 4 3 . 2 3 .3 3 = 3 28 .5 10 .2 21 2 12 .3 24 .5 12 .2 9 .3 3 = 2 21 .3 28 .5 10 2 21 .3 27 .5 12 = 3 5 2 = 3 25