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Bài 4:
a) \(\dfrac{2.7.13}{26.35}=\dfrac{2.7.13}{13.2.7.5}=\dfrac{1}{5}\)
b) \(\dfrac{23.5-23}{4-27}=\dfrac{23.\left(5-1\right)}{-23}=\dfrac{23.4}{-23}=-4\)
c) \(\dfrac{2130-15}{3550-25}=\dfrac{2115}{3525}=\dfrac{3}{5}\)
Bài 1 :
\(-8=\frac{-8}{1}=\frac{-16}{2}=\frac{-24}{3}=\frac{-32}{4}=\frac{-40}{5}\)
\(-2=\frac{-2}{1}=\frac{-4}{2}=\frac{-6}{3}=\frac{-8}{4}=\frac{-10}{5}\)
\(3=\frac{3}{1}=\frac{6}{2}=\frac{9}{3}=\frac{12}{4}=\frac{15}{5}\)
Bài 2 :
a) Để A là phân số thì :
\(n-6\ne0\Rightarrow n\ne6\)
b)\(A=\frac{4}{0-6}=\frac{4}{-6}\)
\(A=\frac{4}{7-6}=4\)
\(A=\frac{4}{-12-6}=\frac{-2}{9}\)
Bài 3 : [ Tương tự bài 2 ]
Bài 4 : [ Suy nghĩ thì ra ]
[ Hoq chắc - có gì sai thông cảm ]
a, \(\dfrac{x}{2}=-\dfrac{5}{y}\Rightarrow xy=-10\Rightarrow x;y\inƯ\left(-10\right)=\left\{\pm1;\pm2;\pm5;\pm10\right\}\)
| x | 1 | -1 | 2 | -2 | 5 | -5 | 10 | -10 |
| y | -10 | 10 | -5 | 5 | -2 | 2 | -1 | 1 |
c, \(\dfrac{3}{x-1}=y+1\Rightarrow\left(y+1\right)\left(x-1\right)=3\Rightarrow x-1;y+1\inƯ\left(3\right)=\left\{\pm1;\pm3\right\}\)
| x - 1 | 1 | -1 | 3 | -3 |
| y + 1 | 3 | -3 | 1 | -1 |
| x | 2 | 0 | 4 | -2 |
| y | 2 | -4 | 0 | -2 |
b: =>xy=12
\(\Leftrightarrow\left(x,y\right)\in\left\{\left(12;1\right);\left(6;2\right);\left(4;3\right)\right\}\)
Bài 1:
a, Ta có:
\(\dfrac{-8}{15}=-\dfrac{5}{18}+-\dfrac{1}{6}\)
b, Ta có:
\(-\dfrac{8}{15}=\dfrac{11}{15}-\dfrac{19}{15}\)
Bài 2:
a, \(\dfrac{11}{13}-\left(\dfrac{5}{12}-x\right)=-\left(\dfrac{15}{18}-\dfrac{11}{13}\right)\)
\(\Rightarrow\dfrac{11}{13}-\dfrac{5}{12}+x=-\dfrac{15}{18}+\dfrac{11}{13}\)
\(\Rightarrow x=-\dfrac{15}{18}+\dfrac{11}{13}+\dfrac{5}{12}-\dfrac{11}{13}\)
\(\Rightarrow x=-\dfrac{15}{8}+\dfrac{5}{12}=-\dfrac{35}{24}\)
b, \(2x-3=x+\dfrac{1}{2}\)
\(\Rightarrow2x-x=\dfrac{1}{2}+3\Rightarrow x=\dfrac{7}{2}\)
Chúc bạn học tốt!!!
\(a)x=1,50505=\dfrac{150505}{100000}\)
\(x=0,0505=\dfrac{505}{10000}\)
\(x=101,101101=\dfrac{101101101}{1000000}\)
\(b)\) Theo bài ra, ta có: \(s=\dfrac{2}{5}\) và \(y=\dfrac{1}{8}s\)
\(\Rightarrow y=\dfrac{1}{8}.\dfrac{2}{5}=\dfrac{1}{20}\)
\(+)y=\dfrac{1}{20};x=3y\)
\(\Rightarrow x=\dfrac{1}{20}.3=\dfrac{3}{20}\)
Vậy \(x=\dfrac{3}{20},y=\dfrac{1}{20}\)