Tính giá trị các biểu thức sau: B = 10 2 9 + 2 3 5 - 6 2 9
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a/\(\frac{4^5.9^4-2.6^9}{2^{10}.3^8+6^8.20}=\frac{\left(2^2\right)^5.\left(3^2\right)^4-2.\left(2.3\right)^9}{2^{10}.3^8+\left(2.3\right)^8.2^2.5}\)
= \(\frac{2^{10}.3^8-2.2^9.3^9}{2^{10}.3^8+2^8.3^8.2^2.5}=\frac{2^{10}.3^8-2^{10}.3^9}{2^{10}.3^8+2^{10}.3^8.5}=\frac{2^{10}.3^8.\left(1-3\right)}{2^{10}.3^8\left(1+5\right)}=\frac{1-3}{1+5}=\frac{-2}{6}=-3\)
\(=\dfrac{2^{19}\cdot3^9-3\cdot3^8\cdot2^{18}\cdot5}{2^{19}\cdot3^9+2^{20}\cdot3^{10}}=\dfrac{-3^{10}\cdot2^{18}}{2^{19}\cdot3^9\cdot7}=-\dfrac{3}{14}\)
A)\(\dfrac{7}{20}-\left(\dfrac{5}{8}-\dfrac{2}{5}\right)\)
\(=\dfrac{7}{20}-\left(\dfrac{25}{40}-\dfrac{16}{40}\right)\)
\(=\dfrac{7}{20}-\dfrac{9}{40}\)
\(=\dfrac{14}{40}-\dfrac{9}{40}=\dfrac{5}{40}=\dfrac{1}{8}\)
B) \(\dfrac{5}{6}+\left(\dfrac{5}{9}-\dfrac{1}{4}\right)\)
\(=\dfrac{5}{6}+\left(\dfrac{20}{36}-\dfrac{9}{36}\right)\)
\(=\dfrac{5}{6}+\dfrac{11}{36}\).
\(=\dfrac{30}{36}+\dfrac{11}{36}=\dfrac{41}{36}\)
C) \(\dfrac{9}{10}-\left(\dfrac{2}{5}-\dfrac{3}{10}\right)+\dfrac{7}{20}\)
\(=\dfrac{9}{10}-\left(\dfrac{4}{10}-\dfrac{3}{10}\right)+\dfrac{7}{20}\)
\(=\dfrac{9}{10}-\dfrac{1}{10}+\dfrac{7}{20}\)
\(=\dfrac{18}{20}-\dfrac{2}{20}+\dfrac{7}{20}=\dfrac{23}{20}\)
a: =7/20-5/8+2/5
=14/40-25/40+16/40
=5/40=1/8
b: =5/6+5/9-1/4
=30/36+20/36-9/36
=41/36
c: =9/10-2/5+3/10+7/20
=12/10-2/5+7/20
=7/20+6/5-2/5
=7/20+4/5
=7/20+16/20
=23/20
\(a\)) \(\left(4^2.4^3\right):2^{10}\)
\(=4^5:2^{10}\)
\(=\left(2^2\right)^5:2^{10}\)
\(=2^{10}:2^{10}\)
\(=1\)
\(b\)) \(\left(0,6\right)^5:\left(0,2\right)^6\)
\(=\left(\frac{3}{5}\right)^5:\left(\frac{1}{5}\right)^6\)
\(=\frac{3^5}{5^5}:\frac{1^6}{5^6}\)
\(=\frac{3^5}{5^5}.5^6\)
\(=\frac{3^5.5^6}{5^5}\)
\(=3^5.5\)
\(=243.5\)
\(=1215\)
\(c\)) \(\left(2^7.9^3\right):\left(6^5.8^2\right)\)
\(=\left[2^7.\left(3^2\right)^3\right]:\left[\left(2.3\right)^5.\left(2^4\right)^2\right]\)
\(=\left(2^7.3^6\right):\left[2^5.3^5.2^8\right]\)
\(=\left(2^7.3^6\right).\left(\frac{1}{2^5.3^5.2^8}\right)\)
\(=\frac{2^7.3^6.1}{\left(2^5.2^8\right).3^5}\)
\(=\frac{2^7.3^6}{2^{13}.3^5}\)
\(=\frac{3}{2^6}\)
\(=\frac{3}{64}\)