rút gọn phân số 19/27
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\(=\dfrac{2^{19}\cdot3^9+2^{18}\cdot3^9\cdot5}{2^{19}\cdot3^9+2^{20}\cdot3^{10}}=\dfrac{2^{18}\cdot3^9\cdot\left(2+5\right)}{2^{19}\cdot3^9\cdot7}=\dfrac{1}{2}\)
\(\frac{2^{19}.27^3+15.4^4.9^4}{6^9.2^{10}+12^{10}}=\frac{2^{19}.3^9+5.2^8.3^9}{2^9.3^9+2^{20}.3^{10}}=\frac{2^8.3^9\left(2^{11}-5\right)}{2^9.3^9\left(1+2^{11}.3\right)}=\frac{2043}{2.6145}=\frac{2043}{12290}\)
\(\frac{2^{19}\cdot27^3+15\cdot4^4\cdot9^4}{6^9\cdot2^{10}+12^{10}}\)
\(=\frac{2^{19}\cdot3^9+3\cdot5\cdot2^8\cdot3^8}{2^9\cdot3^9+2^{20}\cdot3^{10}}\)
\(=\frac{2^8\cdot3^9\left(2^{11}+5\right)}{2^9\cdot3^9\left(2^{11}\cdot3+1\right)}\)
\(=\frac{\left(2^{11}+5\right)}{2\left(2^{11}\cdot3+1\right)}\)
???
\(\dfrac{15}{27}=\dfrac{5}{9};\dfrac{35}{55}=\dfrac{7}{11};\dfrac{101}{909}=\dfrac{1}{9}\)
15/ 27 rút gọn thành 5/9
35/55 rút gọn thành 7/11
101/909 rút gọn thành 1/9
- Các phân số còn lại đều tối giản.
Câu 3:
a) \(\dfrac{12}{36}=\dfrac{12:12}{36:12}=\dfrac{1}{3}\)
\(\dfrac{-16}{20}=\dfrac{-16:4}{20:4}=\dfrac{-4}{5}\)
b) \(\dfrac{21}{105}=\dfrac{21:21}{105:21}=\dfrac{1}{5}\)
\(\dfrac{35}{150}=\dfrac{35:5}{150:5}=\dfrac{7}{30}\)
Câu 4:
a) \(\dfrac{3}{10}+\dfrac{5}{10}=\dfrac{3+5}{10}=\dfrac{8}{10}=\dfrac{4}{5}\)
b) Ta có: \(\left(-27\right)\cdot36+64\cdot\left(-27\right)+23\cdot\left(-100\right)\)
\(=\left(-27\right)\cdot\left(64+36\right)+23\cdot\left(-100\right)\)
\(=-27\cdot100-23\cdot100\)
\(=100\left(-27-23\right)\)
\(=-50\cdot100=-5000\)
c) \(\dfrac{5}{8}+\dfrac{3}{12}=\dfrac{15}{24}+\dfrac{6}{24}=\dfrac{21}{24}=\dfrac{7}{8}\)
d) Ta có: \(\dfrac{-2}{17}+\dfrac{3}{19}+\dfrac{-15}{17}+\dfrac{16}{19}+\dfrac{5}{6}\)
\(=\left(-\dfrac{2}{17}+\dfrac{-15}{17}\right)+\left(\dfrac{3}{19}+\dfrac{16}{19}\right)+\dfrac{5}{6}\)
\(=-1+1+\dfrac{5}{6}\)
\(=\dfrac{5}{6}\)
A= \(\dfrac{10.11.\left(1+5.5+7.7\right)}{11.12.\left(1+5.5+7.7\right)}=\dfrac{10}{12}=\dfrac{5}{6}\)
19/17=19/17:9=2/3
19/27:9=2/3