Tìm x biết
/x-2/=3 72-3./x+1/=9 (x-2).(x+15)=0 (x-3)(x-5)<0 46-(x-11)=-18
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a) \(\frac{5}{12}=\frac{x}{72}\Rightarrow x=\frac{5.72}{12}=30\)
b)\(\frac{x+3}{15}=\frac{1}{3}\)
\(\Rightarrow x+3=\frac{15.1}{3}=5\)
\(\Rightarrow x=5-3=2\)
c)\(\frac{-2}{9}=\frac{x}{72}\Rightarrow x=\frac{-2.72}{9}=-16\)
1) x - 2 = -6
x = -6 + 2
x = -4
2) -5 . x - ( -3 ) =13
-5 . x = 13 + ( -3 )
-5 . x = 10
x = 10 : ( -5 )
x = -2
1)15x-9x+2x=(15-9+2)x=8x=72
x=72:8=9
2)3x+2+3x=3x.32+3x=3x.9+3x.1=3x.(9+1)=3x.10=10
3x=10:10=1
3x=1=30
=>x=0
ko hiểu thì ? đừng k sai nha!
a) Ta có: \(\left(x-2\right)^3-\left(x-3\right)\left(x^2+3x+9\right)+6\left(x+1\right)^2=15\)
\(\Leftrightarrow x^3-6x^2+12x-8-x^3+27+6\left(x^2+2x+1\right)=15\)
\(\Leftrightarrow-6x^2+12x+19+6x^2+12x+6=15\)
\(\Leftrightarrow24x+25=15\)
\(\Leftrightarrow24x=-10\)
hay \(x=-\dfrac{5}{12}\)
b) Ta có: \(2x^3-50x=0\)
\(\Leftrightarrow2x\left(x-5\right)\left(x+5\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=5\\x=-5\end{matrix}\right.\)
c) Ta có: \(5x^2-4\left(x^2-2x+1\right)-5=0\)
\(\Leftrightarrow5x^2-4x^2+8x-4-5=0\)
\(\Leftrightarrow x^2+8x-9=0\)
\(\Leftrightarrow\left(x+9\right)\left(x-1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-9\\x=1\end{matrix}\right.\)
d) Ta có: \(x^3-x=0\)
\(\Leftrightarrow x\left(x-1\right)\left(x+1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=1\\x=-1\end{matrix}\right.\)
e) Ta có: \(27x^3-27x^2+9x-1=1\)
\(\Leftrightarrow\left(3x\right)^3-3\cdot\left(3x\right)^2\cdot1+3\cdot3x\cdot1^2-1^3=1\)
\(\Leftrightarrow\left(3x-1\right)^3=1\)
\(\Leftrightarrow3x-1=1\)
\(\Leftrightarrow3x=2\)
hay \(x=\dfrac{2}{3}\)
\(\frac{x}{3}=\frac{y}{5}=\frac{x+y}{3+5}=\frac{72}{8}=9\)
\(\frac{x}{3}=9=>x=27;\frac{y}{5}=9=>y=45\)
Câu sau tương tự
Chúc bạn học tốt
1) -5x - (-3) = 13
\(\Rightarrow-5x+3=13\)
\(\Rightarrow-5x=10\)
\(\Rightarrow x=-2\)
Vậy: \(x=-2\)
2) 15 - ( x - 7) = -21
\(\Rightarrow15-x+7=-21\)
\(\Rightarrow15+7-x=-21\)
\(\Rightarrow22-x=-21\)
\(\Rightarrow x=-22-21=-43\)
Vậy: \(x=-43\)
3) 45 - ( x - 9) = -35
\(\Rightarrow45-x+9=-35\)
\(\Rightarrow45+9-x=-35\)
\(\Rightarrow54-x=-35\)
\(\Rightarrow x=-54-35=-89\)
Vậy: \(x=-89\)
4)/x-2/=3\(\Rightarrow\)ta có 2 t/h:
t/h1: x-2=3\(\Rightarrow\)x=2+3=5
t/h2: x-2=-3\(\Rightarrow\)x=2+(-3)=-1
Vậy x=5 hoặc -1
|x-2|=3x
\(\Rightarrow\orbr{\begin{cases}x-2=3x\\x-2=-3x\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}-2=3x-x\Rightarrow-2x=2\Rightarrow x=-1\\x-2=-3x\Rightarrow x+3x=2\Rightarrow4x=2\Rightarrow x=2\end{cases}}\)
Vậy x=-1 hoặc x=2
|x-3|-7=13
|x-3|=13+7
|x-3|=20
\(\Rightarrow\orbr{\begin{cases}x-3=20\\x-3=-20\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=20+3=23\\x=-20+3=-17\end{cases}}\)
Vậy x=23 hoặc x=-17
72-(43-|x|)=45
43-|x|=72-45
43-|x|=27
|x|=43-27
|x|=16
=> x=+16
Vậy x=+16
3|x-1|-5=7
3|x-1|=7+5
3|x-1|=12
|x-1|=12:3
|x-1|=4
\(\Rightarrow\orbr{\begin{cases}x-1=4\Rightarrow x=4+1=5\\x-1=-4\Rightarrow x=-4+1=-3\end{cases}}\)
Vậy x=5 hoặc x=-3
(7-x )(x+9)=0
* 7-x=0 * x+9=0
x=7-0 x=0-9
x=7 x=-9
Vậy x=7 hoặc x=-9
(x-2)(x+15)=0
* x-2=0 * x+15=0
x=0+2 x=0-15
x=2 x=-15
Vậy x=2 hoặc x=-15
-12(x-5)+7(3-x)=5
-12x+60+21-7x=5
-12x-7x=5-60-21
-19x=-76
x=-76:(-19)
x=4
Vậy x=4
2x2-3=29
2x2=29+3
2x2=32
x2=32:2
x2=16
x2=42
=> x=4
Vậy x=4
\(\left|x-3\right|-7=13\)
\(\left|x-3\right|=20\)
\(\Leftrightarrow\orbr{\begin{cases}x-3=20\\x-3=-20\end{cases}\Leftrightarrow\orbr{\begin{cases}x=23\\x=-17\end{cases}}}\)
vậy x=23 hoặc x=-17
\(\left(7-x\right)\left(x+9\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}7-x=0\\x+9=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=7\\x=-9\end{cases}}}\)
vậy x=7 hoặc x=-9
\(\left(x-2\right)\left(x+15\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}x-2=0\\x+15=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=2\\x=-15\end{cases}}}\)
vậy x=2 hoặc x=-15
\(2x^2-3=29\)
\(2x^2=32\)
\(x^2=16\)
\(\Rightarrow x=\pm4\)