Rút gọn: 17 . 5 - 17 3 - 20
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\(\dfrac{15}{27}=\dfrac{5}{9};\dfrac{35}{55}=\dfrac{7}{11};\dfrac{101}{909}=\dfrac{1}{9}\)
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) \(H=\sqrt{9-\sqrt{17}}.\sqrt{9+\sqrt{17}}=\sqrt{\left(9-\sqrt{17}\right)\left(9+\sqrt{17}\right)}\)
\(=\sqrt{81-17}=\sqrt{64}=8\)
b) \(K=\left(\sqrt{20}-3\sqrt{5}+\sqrt{80}\right).\sqrt{5}\)
\(=\sqrt{20}.\sqrt{5}-3\sqrt{5}.\sqrt{5}+\sqrt{80}.\sqrt{5}\)
\(=\sqrt{100}-3.5+\sqrt{400}=\sqrt{10^2}-15+\sqrt{20^2}\)
\(=10-15+20=15\)
\(H=\sqrt{9-\sqrt{17}}\cdot\sqrt{9+\sqrt{17}}\)
\(=\sqrt{\left(9-\sqrt{17}\right)\left(9+\sqrt{17}\right)}\)
\(=\sqrt{9^2-\left(\sqrt{17}\right)^2}\)
\(=\sqrt{81-17}\)
\(=\sqrt{64}=8\)
\(K=\left(\sqrt{20}-3\sqrt{5}+\sqrt{80}\right)\cdot\sqrt{5}\)
\(=\sqrt{20}\cdot\sqrt{5}-3\sqrt{5}\cdot\sqrt{5}+\sqrt{80}\cdot\sqrt{5}\)
\(=\sqrt{20\cdot5}-3\sqrt{5\cdot5}+\sqrt{80\cdot5}\)
\(=\sqrt{100}-3\sqrt{25}+\sqrt{400}\)
\(=10-3\cdot5+20\)
\(=15\)
bạn ghi kiểu phân số theo chiều thẳng đứng được không, như vầy mình nhìn tưởng là chia
135.173.a9.(13.172.a3)
= 135.173.13.172.a9.a3
= (135.13).(173.172).(a9.a3)
= 136.175.a12
a) \(\dfrac{8,5-8,2}{16}=\dfrac{0,3}{16}=\dfrac{0,3\cdot10}{16\cdot10}=\dfrac{3}{160}\)
b) \(\dfrac{17\cdot5-17}{3-20}=\dfrac{17\cdot\left(5-1\right)}{-17}=\dfrac{1\cdot4}{-1}=-4\)
a)
\(\dfrac{8\cdot5-8\cdot2}{16}=\dfrac{8\left(5-2\right)}{16}=\dfrac{3}{2}\)
b)
\(\dfrac{17\cdot5-17}{3-20}=\dfrac{17\left(5-1\right)}{-17}=\dfrac{4}{-1}=-4\)
17 . 5 - 17 3 - 20 = 17 ( 5 - 1 ) - 17 = 5 - 1 - 1 = - 4