\(\frac{72-x}{3}=\frac{x-18}{5}\)
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![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{72-x}{3}=\frac{x-18}{5}\)
\(\Rightarrow\frac{\left(72-x\right).5}{15}=\frac{3\left(x-18\right)}{15}\)
\(\Rightarrow\left(72-x\right).5=3\left(x-18\right)\)
\(\Rightarrow360-5x=3x-54\)
\(\Rightarrow-3x-5x=-360-54\)
\(\Rightarrow-8x=-414\)
\(\Rightarrow x=51,75\)
+) Vì \(\frac{72-x}{3}=\frac{x-18}{5}\)
\(\Rightarrow5\left(72-x\right)=3\left(x-18\right)\)
\(5.72-5x=3x-3.18\)
\(360-5x=3x-54\)
\(-5x-3x=-54-360\)
\(-8x=-414\)
\(x=-414:\left(-8\right)\)
\(x=51,75\)
Vậy x = 51,75
![](https://rs.olm.vn/images/avt/0.png?1311)
b, \(\frac{72-x}{3}=\frac{x-18}{5}\)
\(\Rightarrow\left(72-x\right).5=\left(x-18\right).3\)
\(\Rightarrow72.5-5x=3x-18.3\)
\(\Rightarrow360-5x=3x-54\)
\(\Rightarrow360+54=3x+5x\)
\(\Rightarrow414=8x\)
\(\Rightarrow x=414:8\)
\(\Rightarrow x=51,75\)
Vậy \(x=51,75\)
a, \(3\frac{4}{5}:2x=0,25:2\frac{2}{3}\)
\(\frac{19}{5}:2x=\frac{1}{4}:\frac{8}{3}\)
\(\frac{19}{5}:2x=\frac{3}{32}\)
\(2x=\frac{19}{5}:\frac{3}{32}\)
\(2x=\frac{608}{15}\)
\(x=\frac{304}{15}\)
Thay x vào biểu thức thì nó không có bằng nhau. Bạn xem lại đề nha.
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có : \(\frac{72-x}{3}=\frac{x-18}{5}\)
\(\Rightarrow5\left(72-x\right)=3\left(x-18\right)\)
\(\Rightarrow360-5x=3x-54\)
\(\Rightarrow360-54=5x-3x\)
\(\Rightarrow306=2x\) hay \(2x=306\)
x = 306 : 2 \(\Rightarrow x=153\)
Vậy x = 153
Mình không chắc chắn lắm ! Bạn thử kiểm tra lại nha !
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có: \(\dfrac{-5}{x}=\dfrac{-y}{8}=\dfrac{-18}{72}\)
\(\Leftrightarrow\left\{{}\begin{matrix}\dfrac{-5}{x}=-\dfrac{18}{72}=\dfrac{-1}{4}\\\dfrac{-y}{8}=\dfrac{-18}{72}=\dfrac{-1}{4}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=20\\y=2\end{matrix}\right.\)
Vậy: (x,y)=(20;2)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{-5}{x}=\frac{-y}{8}=\frac{18}{72}\)
\(\Leftrightarrow\frac{-5}{x}=\frac{-y}{8}=\frac{1}{4}\)
\(\Leftrightarrow\orbr{\begin{cases}-\frac{5}{x}=\frac{1}{4}\\-\frac{y}{8}=\frac{1}{4}\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=-5.4:1\\-y=8.1:4\end{cases}\Leftrightarrow\orbr{\begin{cases}x=-20\\-y=2\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=-20\\y=-2\end{cases}}}\)
vậy x=-20 và y=-2
![](https://rs.olm.vn/images/avt/0.png?1311)
-18/72=-2/8=-4/16. Suy ra x=-4
-5/x=-2/8.Suy ra -5.8=-2.x
-40=-2x
x=20
![](https://rs.olm.vn/images/avt/0.png?1311)
<=> (x-18/74 - 1)+(x-20/72 - 1)+(x-22/70 - 1) = 0
<=> x-92/74 + x-92/72 + x-92/70 = 0
<=> (x-92).(1/74+1/72+1/70) = 0
<=> x-92 = 0 ( vì 1/74 + 1/72 + 1/70 > 0 )
<=> x=92
Vậy S = {92}
Tk mk nha
Ta có :
\(\frac{x-18}{74}+\frac{x-20}{72}+\frac{x-22}{70}=3\)
\(\Leftrightarrow\)\(\left(\frac{x-18}{74}-1\right)+\left(\frac{x-20}{72}-1\right)+\left(\frac{x-22}{70}-1\right)=3-3\)
\(\Leftrightarrow\)\(\frac{x-92}{74}+\frac{x-92}{72}+\frac{x-92}{70}=0\)
\(\Leftrightarrow\)\(\left(x-92\right)\left(\frac{1}{74}+\frac{1}{72}+\frac{1}{70}\right)=0\)
Vì \(\left(\frac{1}{74}+\frac{1}{72}+\frac{1}{70}\right)\ne0\)
\(\Rightarrow\)\(x-92=0\)
\(\Rightarrow\)\(x=92\)
Vậy \(x=92\)
Chúc bạn học tốt
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{72-x}{x-18}=\frac{x}{5}\)
=> 5(72 - x) = x(x - 18)
=> 360 - 5x = x2 - 18x
=> x2 - 13x = 360
=> x2 - 6,5x - 6,5x + 42,25 = 360 + 42,25
=> x(x - 6,5) - 6,5(x - 6,5) = 402,25
=> (x - 6,5)2 = 402,25
=> \(\orbr{\begin{cases}x=\sqrt{402,25}+6,5\\x=-\sqrt{402,25}+6,5\end{cases}}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có :
-5/x = -18/72
=> -5 . 72 = -18 . x
=> -360 = -18 . x
=> x = -360 :- 18
=> x = 20
Thay x = 20 ta được :
-5/20 = y/16
=> -5 . 16 = 20 . y
=> -80 = 20 . y
=> y = -80 : 20
=> y = -4
Vậy x = 20 , y = -4
Chúc bạn học giỏi nha !!!
Dấu " / " là chia
TK mình nha !!! ^_^
\(\frac{72-x}{3}=\frac{x-18}{5}\)
\(\Rightarrow5\left(72-x\right)=3\left(x-18\right)\)
\(\Rightarrow360-5x=3x-54\)
\(\Rightarrow-5x-3x=-54-360\)
\(\Rightarrow-8x=-414\)
\(\Rightarrow x=207\)