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Câu a:
\(\frac27\) + \(\frac{-3}{8}\) + \(\frac{11}{7}\) + \(\frac17\) + \(\frac{5}{-8}\)
= (\(\frac27+\frac{11}{7}+\frac17\)) -(\(\frac38\) + \(\frac58\))
= (\(\frac{13}{7}+\frac17\)) - \(\frac88\)
= \(\frac{14}{7}-1\)
= 2 - 1
= 1
Câu b:
\(\frac{3}{17}+\frac{-5}{13}+\frac{-18}{35}+\frac{14}{17}+\frac{17}{-35}+\frac{-8}{13}\)
= (\(\frac{3}{17}+\frac{14}{17}\)) - (\(\frac{5}{13}\) + \(\frac{8}{13}\)) - (\(\frac{18}{35}+\frac{17}{35}\))
= \(\frac{17}{17}-\frac{18}{18}-\) \(\frac{35}{35}\)
= 1 - 1 - 1
= 0 - 1
= -1
mình ghi nhầm nên các bạn cứ hết hai phân số là một câu nhé ví dụ như \(\dfrac{-5}{8}\):\(\dfrac{15}{4}\)
\(\dfrac{-15}{17}\):\(\dfrac{25}{34}\)=\(\dfrac{-15}{17}\)x\(\dfrac{34}{25}\)=\(\dfrac{-510}{452}\)=\(\dfrac{-255}{226}\)
a: 7/30=21/90
8/45=16/90
11/90=11/90
b: -4/5=-168/210
1/6=35/210
-9/7=-270/210
c: -7/24=-21/72
11/12=66/72
-23/36=-46/72
d: 17/30=85/150
-22/75=-44/150
5=750/150
a: \(\Leftrightarrow\dfrac{8}{5}+\dfrac{2}{5}\cdot x=\dfrac{16}{5}\)
=>2/5x=8/5
=>x=4
b: \(\Leftrightarrow\left(\dfrac{1}{24}-\dfrac{1}{25}+\dfrac{1}{25}-\dfrac{1}{26}+...+\dfrac{1}{39}-\dfrac{1}{40}\right)\cdot120+\dfrac{1}{3}x=-4\)
\(\Leftrightarrow x\cdot\dfrac{1}{3}+2=-4\)
=>1/3x=-6
=>x=-18
c: =>2|x-1/3|=0,24-4/5=-0,56<0
a)\(\dfrac{2}{5}-\dfrac{3}{7}+\dfrac{9}{45}\\ =\dfrac{2}{5}-\dfrac{3}{7}+\dfrac{1}{5}\\ =\dfrac{14-15+1}{35}\\ =\dfrac{0}{35}=0\)
b)\(\dfrac{5}{15}+\dfrac{14}{25}-\dfrac{12}{9}+\dfrac{2}{7}+\dfrac{11}{25}\\ =\left(\dfrac{1}{3}-\dfrac{4}{3}\right)+\left(\dfrac{14}{25}+\dfrac{11}{25}\right)+\dfrac{2}{7}\\ =-1+1+\dfrac{2}{7}\\ =0+\dfrac{2}{7}=\dfrac{2}{7}\)
a: \(=\left(\dfrac{17}{10}+\dfrac{70}{10}-\dfrac{87}{10}\right):\left(\dfrac{23}{4}-\dfrac{11}{4}+\dfrac{9}{25}\right)\cdot\left(12,98\cdot0,25\right)+12,5\)
\(=0:\left(3+\dfrac{9}{25}\right)\cdot\left(12,98+0,25\right)+12,5\)
=12,5
b: \(=\dfrac{13}{12}\cdot\dfrac{27}{5}\cdot2\cdot\dfrac{34}{9}\cdot2\cdot\dfrac{2}{17}\)
\(=\dfrac{13}{12}\cdot2\cdot\dfrac{27}{5}\cdot\dfrac{34}{9}\cdot\dfrac{4}{17}\)
\(=\dfrac{13}{6}\cdot\dfrac{27}{5}\cdot\dfrac{8}{9}=\dfrac{8}{6}\cdot3\cdot\dfrac{13}{5}=4\cdot\dfrac{13}{5}=\dfrac{52}{5}\)
\(F=\dfrac{12-\dfrac{36}{17}+\dfrac{24}{25}}{15-\dfrac{45}{17}+\dfrac{30}{25}}=\dfrac{12\left(1-\dfrac{3}{17}+\dfrac{2}{25}\right)}{15\left(1-\dfrac{3}{17}+\dfrac{2}{25}\right)}\)
\(=\dfrac{12}{15}=\dfrac{4}{5}\)
\(F=\dfrac{12-\dfrac{36}{17}+\dfrac{24}{25}}{15-\dfrac{45}{17}+\dfrac{30}{25}}\)
\(F=\dfrac{12.1-\dfrac{12.3}{17}+\dfrac{12.2}{25}}{15.1-\dfrac{15.3}{17}+\dfrac{15.2}{25}}\)
\(F=\dfrac{12.\left(1-\dfrac{3}{17}+\dfrac{2}{25}\right)}{15.\left(1-\dfrac{3}{17}+\dfrac{2}{25}\right)}\)
\(F=\dfrac{12.1}{15.1}\)
\(F=\dfrac{12}{15}\)
\(F=\dfrac{4}{5}\)