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\(\frac{x}{27}-\frac{2}{9}=\frac{6}{18}\)
\(\frac{x}{27}=\frac{3}{9}+\frac{2}{9}\)
\(\frac{x}{27}=\frac{5}{9}\)
\(\frac{x}{27}=\frac{15}{27}\)
=> x = 15
( 4,5 - \(\dfrac{4}{7}\) \(x\)): \(\dfrac{5}{6}\) = 0,6
(4,5 - \(\dfrac{4}{7}\)\(x\)) = 0,6 \(\times\) \(\dfrac{5}{6}\)
4,5 - \(\dfrac{4}{7}\) \(x\) = 0,5
\(\dfrac{4}{7}x\) = 4,5 - 0,5
\(\dfrac{4}{7}x\) = 4
\(x\) = 4 : \(\dfrac{4}{7}\)
\(x\) = 7
\(\frac{y}{3}-\frac{1}{x}=\frac{1}{3}\)
\(\Leftrightarrow\frac{xy}{3x}-\frac{3}{3x}=\frac{x}{3x}\)
\(\Leftrightarrow xy-3=x\)
\(\Leftrightarrow xy-x=3\)
\(\Leftrightarrow x\left(y-1\right)=3=\left(-1\right).\left(-3\right)=3.1\)( vì x, y là các số nguyên )
\(TH1:\)
\(\orbr{\begin{cases}x=1\\y-1=3\end{cases}}\Rightarrow\orbr{\begin{cases}x=1\\y=4\end{cases}}\)
\(\orbr{\begin{cases}x=3\\y-1=1\end{cases}\Rightarrow\orbr{\begin{cases}x=3\\y=2\end{cases}}}\)
\(TH2:\)
\(\orbr{\begin{cases}x=-1\\y-1=-3\end{cases}}\Rightarrow\orbr{\begin{cases}x=-1\\y=-2\end{cases}}\)
\(\orbr{\begin{cases}x=-3\\y-1=-1\end{cases}\Rightarrow}\orbr{\begin{cases}x=-3\\y=0\end{cases}}\)
Vậy .......
Giải: Có y/3-1/x=1/3
y/3-1/3=1/x
Suy ra y-1/3=1/x
Suy ra (y-1).x=3
Suy ra y-1 và x thuộc Ư(3)
Vì x,y thuộc Z
Do đó ta có bảng giá trị:
y-1 | 1 | 3 | -1 | -3 |
x | 3 | 1 | -3 | -1 |
y | 2 | 4 | 0 | -2 |
Vậy (x,y)= {...........}
nha
a) \(83+158+17+142.\)
\(=\left(83+17\right)+\left(158+142\right)\) \(=100+300=400.\)
b) \(\text{57 + 725 + 605 - 57}.\)
\(=\left(57-57\right)+\left(725+605\right)\) \(=1330.\)
c) \(14.42-32.14=14.\left(42-32\right)=14.10=140.\)
d) \(12.35+35.182-35.94=35\left(12+182-94\right)=35.100=3500.\)
e) \(58.75+58.50-58.25=58\left(75-25+50\right)=58.100=5800.\)
Ta nhận thấy vế trái có 100 số hạng
=> \(\left(x+x+...+x\right)+\left(1+2+...+100\right)=5500\)
<=> \(100x+\frac{100.101}{2}=5500\)
<=> \(100x+5050=5500\)
<=> \(x=4,5\)
\(\left(x+1\right)+\left(x+2\right)+\left(x+3\right)+...+\left(x+100\right)=5550\)
\(< =>x+1+x+2+x+3+...+x+100=5550\)
\(< =>100x+\frac{100\left(100+1\right)}{2}=5550\)
\(< =>100x+\frac{10100}{2}=5550\)
\(< =>100x+5050=5550\)
\(< =>100x=500< =>x=\frac{500}{100}=5\)
a: -7/15=-28/60
5/12=25/60
b: 1/5=6/30
-2/3=-20/30
7/10=21/30
\(-\dfrac{7}{15}=\dfrac{-7.4}{15.4}=\dfrac{-28}{60};\dfrac{5}{12}=\dfrac{5.5}{12.5}=\dfrac{25}{60}\)
\(\dfrac{1}{5}=\dfrac{1.6}{5.6}=\dfrac{6}{30};\dfrac{-2}{3}=\dfrac{-2.10}{3.10}=\dfrac{-20}{30};\dfrac{7}{10}=\dfrac{7.3}{10.3}=\dfrac{21}{30}\)
b) \(\frac{-5}{7}\).\(\frac{2}{11}\)--\(\frac{-5}{7}\).\(\frac{9}{11}\)+ \(1\frac{5}{7}\)
= \(\frac{-5}{7}\). (\(\frac{2}{11}\)--\(\frac{9}{11}\)) + \(1\frac{5}{7}\)
= \(\frac{-5}{7}\). 1 + \(1\frac{5}{7}\)
=\(\frac{-5}{7}\)+\(\frac{10}{7}\)
=\(\frac{5}{7}\)
c)\(11\frac{3}{13}\)-- (\(2\frac{4}{7}\)+\(5\frac{3}{13}\))
=\(11\frac{3}{13}\)-- \(2\frac{4}{7}\)-- \(5\frac{3}{13}\)
=(\(11\frac{3}{13}\)-- \(5\frac{3}{13}\)) -- \(2\frac{4}{7}\)
=6 -- \(\frac{18}{7}\)
=\(\frac{42}{7}\)--\(\frac{18}{7}\)
=\(\frac{24}{7}\)