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(x+2).(y-3)=-3=-1.3=1.(-3)
Vì x,y thuộc Z nên ( x+2) và (y+3) thuộc Z
Ta có bảng:
x+2 | -1 | 1 | -3 | 3 |
y+3 | 3 | -3 | 1 | -1 |
x | -3 | -1 | -5 | 1 |
y | 0 | -6 | -2 | -4 |
Vậy nếu x = - 3 thì y = 0
nếu x = -1 thì y =- 6
nếu x = - 5 thì y = - 2
nếu x = 1 thì y = - 4
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1 - 2 + 3 - 4 + 5 - 6 + ......... + 159 - 160 ( có 160 số )
= - 1 + ( - 1 ) + ( - 1 ) + .......... + ( - 1 ) ( có 80 số - 1 )
= - 1 . 80
= - 80
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\(\frac{x}{4}=\frac{y}{3}\)
\(\Rightarrow\frac{x+y}{4+3}=\frac{x}{4}=\frac{y}{3}\) mà x + y = 14
\(\Rightarrow\frac{14}{7}=\frac{x}{4}=\frac{y}{3}\)
\(\Rightarrow2=\frac{x}{4}=\frac{y}{3}\)
\(\Rightarrow\hept{\begin{cases}x=2\cdot4=8\\y=2\cdot3=6\end{cases}}\)
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Ta có :
\(\frac{2}{3}\)là phân số tối giản
nên \(\frac{-x}{6}=\frac{2}{3}\)
\(\Rightarrow\text{-x.3=2.6}\)
\(\Rightarrow-x.3=12\)
\(\Rightarrow x=-4\)
Tương tự \(\frac{14}{-y}=\frac{2}{3}\)
\(14.3=2.y\)
\(\Leftrightarrow42=2y\)
\(\Rightarrow y=21\)
Và \(\frac{z}{60}=\frac{2}{3}\)
\(\Leftrightarrow3z=2.60\)
\(\Leftrightarrow3z=120\)
\(\Rightarrow z=40\)
Vậy x=-4
y=21
z=40
chúc bạn học tốt !
\(\frac{-x}{6}=\frac{14}{-y}=\frac{z}{60}=\frac{2}{3}\)
Xét \(\frac{-x}{6}=\frac{2}{3}\)
\(\Leftrightarrow-x.3=12\Leftrightarrow-x=4\Leftrightarrow x=-4\)
Xét \(\frac{14}{-y}=\frac{2}{3}\)
\(\Leftrightarrow14.3=-y.2\Leftrightarrow42=-y.2\Leftrightarrow y=-21\)
Xét \(\frac{z}{60}=\frac{2}{3}\)
\(\Leftrightarrow z.3=120\Leftrightarrow z=40\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 9:
Ta có: \(\dfrac{12}{-6}=\dfrac{x}{5}=\dfrac{-y}{3}=\dfrac{z}{-17}=\dfrac{-t}{-9}\)
\(\Leftrightarrow\dfrac{x}{5}=\dfrac{-y}{3}=\dfrac{-z}{17}=\dfrac{t}{9}=-2\)
\(\Leftrightarrow\left\{{}\begin{matrix}\dfrac{x}{5}=-2\\\dfrac{-y}{3}=-2\\\dfrac{-z}{17}=-2\\\dfrac{t}{9}=-2\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=-10\\-y=-6\\-z=-34\\t=-18\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=-10\\y=6\\z=34\\t=-18\end{matrix}\right.\)
Vậy: (x,y,z,t)=(-10;6;34;-18)
Bài 11:
Ta có: \(\dfrac{-7}{6}=\dfrac{x}{18}=\dfrac{-98}{y}=\dfrac{-14}{z}=\dfrac{t}{102}=\dfrac{u}{-78}\)
\(\Leftrightarrow\dfrac{x}{18}=\dfrac{-98}{y}=\dfrac{-14}{z}=\dfrac{t}{102}=\dfrac{u}{-78}=\dfrac{-7}{6}\)
Ta có: \(\dfrac{x}{18}=\dfrac{-7}{6}\)
\(\Leftrightarrow x=\dfrac{18\cdot\left(-7\right)}{6}=-21\)
Ta có: \(\dfrac{-98}{y}=\dfrac{-7}{6}\)
\(\Leftrightarrow y=\dfrac{-98\cdot6}{-7}=84\)
Ta có: \(\dfrac{-14}{z}=\dfrac{-7}{6}\)
\(\Leftrightarrow z=\dfrac{-14\cdot6}{-7}=12\)
Ta có: \(\dfrac{u}{-78}=\dfrac{-7}{6}\)
\(\Leftrightarrow u=\dfrac{-78\cdot\left(-7\right)}{6}=\dfrac{78\cdot7}{6}=91\)
Ta có: \(\dfrac{t}{102}=\dfrac{-7}{6}\)
\(\Leftrightarrow t=\dfrac{-7\cdot102}{6}=-7\cdot17=-119\)
Vậy: (x,y,z,t,u)=(-21;84;12;-119;91)
![](https://rs.olm.vn/images/avt/0.png?1311)
dang toan nay em chua hieu hay giup em giai bai
xin cam on
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 2:
\(a,\dfrac{2}{x}=\dfrac{x}{8}\\ \Rightarrow x.x=8.2\\ \Rightarrow x^2=16\\ \Rightarrow x=\pm4\)
\(b,\dfrac{2x-9}{240}=\dfrac{39}{80}\\ \Rightarrow80\left(2x-9\right)=240.39\\ \Rightarrow160x-720=9360\\ \Rightarrow160x=10080\\ \Rightarrow x=63\)
\(c,\dfrac{x-1}{9}=\dfrac{8}{3}\\ \Rightarrow3\left(x-1\right)=8.9\\ \Rightarrow3\left(x-1\right)=72\\ \Rightarrow x-1=24\\ \Rightarrow x=25\)
![](https://rs.olm.vn/images/avt/0.png?1311)
ta có:
\(\frac{-x}{6}=\frac{-14}{9}=\frac{z}{60}=\frac{2}{-3}\)
\(\frac{-x.30}{180}=\frac{-280}{180}=\frac{z.3}{180}=\frac{-120}{180}\)
=>-x .30=-120
z.3=-120(vì -280 không chia hết cho 30 và 3)
=> x =-4
z=-40
1/ Ta xem phần này trước: \(-\frac{6}{y}=\frac{6}{7}\left(rutgon\right)\)
\(\Rightarrow y=7.\left(-6\right):6=-7\)
Quay lại lúc đầu: \(\frac{x}{14}=\frac{6}{7}\)
\(\Rightarrow x=6.14:7=12\)
2/ \(\Leftrightarrow x-\frac{14}{x}=-3+\frac{2}{3}\)
\(\Leftrightarrow\frac{3x-2}{3}=-\frac{7}{3}\left(quydong\right)\)
\(\Leftrightarrow3x-2=-7\)
Giải nốt hộ nha lười quá
\(\frac{x}{14}=\frac{-6}{y}=\frac{6}{7}\)
Ta có :\(\frac{-6}{y}=\frac{6}{7}\)=>\(y=\frac{-6.7}{6}=-7\)
\(\frac{x}{14}=\frac{6}{7}\)=>\(x=\frac{6.14}{7}\)=12
2/\(\frac{x-2}{3}=\frac{14}{x-3}\)
=>(x-2).(x-3)=14.3=42
Tự làm nhé