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D
2
BN
12 tháng 9 2019
a, Tự chép đề bài :v
=> 22x-3 = ( 83. 165 ) : 410
22x-3 = ( 29. 220 ) : 220
22x-3 = 229 : 220
22x-3 = 29
=> 2x - 3 = 9
2x = 9 + 3
2x = 12
x = 6
Vậy....
b, 7. 2x = 29 + 5. 28
7. 2x = 1792
2x = 1792 : 7
2x = 256
2x = 28
=> x = 8
Vậy ....
M
12 tháng 9 2019
a \(\frac{2^{2x-3}}{4^{10}}=8^3.16^5\)
\(\Leftrightarrow\frac{2^{2x-3}}{4^{10}}=2^{29}\)
\(\Leftrightarrow2^{2x-3}=2^{29}.4^{10}\)
\(\Leftrightarrow2^{2x-3}=2^{49}\)
\(\Leftrightarrow2x-3=49\)
\(\Leftrightarrow x=26\)
b \(7.2^x=2^9+5.2^8\)
\(\Leftrightarrow7.2^x=2^8.(2+5)\)
\(\Leftrightarrow7.2^x=7.2^8\)
\(\Leftrightarrow x=7\)
HT
8 tháng 8 2015
Nếu phân số thứ 2 là \(\frac{1}{10.17}\) thì làm như vậy nè
\(\frac{1}{3.10}+\frac{1}{10.17}+...+\frac{1}{73.80}-\frac{1}{2.9}-\frac{1}{9.16}-\frac{1}{16.23}-\frac{1}{23.30}\)
= \(\frac{1}{7}\left(\frac{1}{3}-\frac{1}{10}+\frac{1}{10}-\frac{1}{17}+...+\frac{1}{73}-\frac{1}{80}\right)-\left(\frac{1}{2.9}+\frac{1}{9.16}+\frac{1}{16.23}+\frac{1}{23.30}\right)\)
= \(\frac{1}{7}\left(\frac{1}{3}-\frac{1}{80}\right)-\frac{1}{7}\left(\frac{1}{2}-\frac{1}{9}+\frac{1}{9}-\frac{1}{16}+\frac{1}{16}-\frac{1}{23}+\frac{1}{23}-\frac{1}{30}\right)\)
= \(\frac{1}{7}.\frac{77}{240}-\frac{1}{7}\left(\frac{1}{2}-\frac{1}{30}\right)=\frac{1}{7}.\frac{77}{240}-\frac{1}{7}.\frac{7}{15}\)
= \(\frac{11}{240}-\frac{1}{15}\)
= \(-\frac{1}{48}\)
5 tháng 7 2018
\(\frac{1}{15}\)chứ ko phải \(\frac{1}{5}\)nha các bạn
5 tháng 7 2018
\(\frac{1}{5}+\frac{9}{10}+\frac{14}{15}-\frac{1}{9}-\frac{20}{10}+\frac{1}{157}\)
\(=\frac{3}{15}+\frac{9}{10}+\frac{14}{15}-\frac{1}{9}-\frac{20}{10}+\frac{1}{157}\)
\(=\left(\frac{3}{15}+\frac{14}{15}\right)+\left(\frac{9}{10}-\frac{20}{10}\right)-\frac{1}{9}+\frac{1}{157}\)
\(=\frac{17}{15}+\frac{-11}{10}-\frac{1}{9}+\frac{1}{157}\)
\(=\left(\frac{51}{45}-\frac{5}{45}\right)+\frac{-11}{10}+\frac{1}{157}\)
\(=\frac{46}{45}+\frac{-11}{10}+\frac{1}{157}\)
\(=\left(\frac{92}{90}+\frac{-99}{90}\right)+\frac{1}{157}\)
\(=\frac{-1099}{14130}+\frac{90}{14130}\)
\(=\frac{-1099}{14130}\)
23 tháng 7 2017
B. 1/3 - 1/3 - 3/5 +3/5 + 5/7 - 5/7 + 9/11 - 9/11 -11/13 + 11/ 13 + 7/9 + 13/15
= 0 -0-0-0-0+7/9 +13/15
= 74/45
21 tháng 6 2020
a) Ta có: \(\frac{3}{8}-\frac{1}{5}+\frac{3}{40}\)
\(=\frac{15}{40}-\frac{8}{40}+\frac{3}{40}\)
\(=\frac{10}{40}=\frac{1}{4}\)
b) Ta có: \(\frac{21}{4}\cdot\frac{3}{8}+\frac{43}{4}\cdot\frac{3}{8}-4\cdot\frac{1}{2}\)
\(=\frac{3}{8}\left(\frac{21}{4}+\frac{43}{4}\right)-2\)
\(=\frac{3}{8}\cdot16-2\)
\(=6-2=4\)
c) Ta có: \(\frac{-5}{9}+\frac{7}{15}+\frac{-2}{11}+\frac{4}{-9}+\frac{8}{15}\)
\(=\left(\frac{-5}{9}+\frac{-4}{9}\right)+\left(\frac{7}{15}+\frac{8}{15}\right)+\frac{-2}{11}\)
\(=-1+1+\frac{-2}{11}\)
\(=\frac{-2}{11}\)
d) Ta có: \(125\%\cdot\left(\frac{-1}{2}\right)^2:\left(1\frac{5}{6}-1.5\right)+2016^0\)
\(=\frac{5}{4}\cdot\frac{1}{4}:\left(\frac{11}{6}-\frac{3}{2}\right)+1\)
\(=\frac{5}{16}\cdot3+1\)
\(=\frac{15}{16}+\frac{16}{16}=\frac{31}{16}\)
HT
25 tháng 7 2017
\(=\frac{16}{5}.\frac{15}{16}-\left(\frac{3}{4}+\frac{2}{7}\right):\left(\frac{-29}{28}\right)\)
\(=3-\left(\frac{21}{28}+\frac{8}{28}\right):\left(\frac{-29}{28}\right)\)
\(=3-\left(\frac{29}{28}\right).\left(\frac{-28}{29}\right)\)
\(=3-\left(-1\right)\)
\(=4\)
b) \(=\left(\frac{1}{4}+\frac{25}{2}-\frac{5}{16}\right):\left(12-\frac{7}{12}:\left(\frac{3}{8}-\frac{1}{12}\right)\right)\)
\(=\left(\frac{4}{16}+\frac{200}{16}-\frac{5}{16}\right):\left(12-\frac{7}{12}:\left(\frac{3.3}{2.3.4}-\frac{2}{2.3.4}\right)\right)\)
\(=\left(\frac{199}{16}\right):\left(12-\frac{7}{12}:\left(\frac{9}{24}-\frac{2}{24}\right)\right)\)
\(=\frac{199}{16}:\left(12-\frac{7}{12}.\frac{24}{7}\right)\)
\(=\frac{199}{16}:\left(12-2\right)\)
\(=\frac{199}{16}:10\)
\(=\frac{199}{160}\)
c) \(\left(\frac{-3}{5}+\frac{5}{11}\right):\frac{-3}{7}+\left(\frac{-2}{5}+\frac{6}{5}\right):\frac{-3}{7}\)
\(\left(\frac{-33}{55}+\frac{25}{55}\right):\frac{-3}{7}+\left(\frac{4}{5}\right):\frac{-3}{7}\)
\(\left(\frac{-8}{55}\right).\frac{-7}{3}+\frac{4}{5}.\frac{-7}{3}\)
\(\frac{-7}{3}\left(\frac{-8}{55}+\frac{4}{5}\right)\)
\(\frac{-7}{3}.\frac{36}{55}=\frac{-84}{55}\)
= 2/3 bn nhé
T mk nha!!!
\(\frac{3.17-9}{3.16+15}\)
=\(\frac{3.\left(16+1\right)-9}{3.16+15}\)
=\(\frac{3.16+3.1-9}{3.16+15}\)
=\(\frac{3.16+3-9}{3.16+15}\)
=\(\frac{3-9}{15}\)(vì đã triệt tiêu 3.16)
=\(\frac{-6}{15}\)=\(\frac{-2}{5}\)