tìm x, biết :
3-1/5x=0
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a) \(\Rightarrow x\left(x+3\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=0\\x=-3\end{matrix}\right.\)
b) \(\Rightarrow x\left(x^2-4\right)=0\Rightarrow x\left(x-2\right)\left(x+2\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=0\\x=2\\x=-2\end{matrix}\right.\)
c) \(\Rightarrow\left(x-1\right)\left(5x-1\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=1\\x=\dfrac{1}{5}\end{matrix}\right.\)
d) \(\Rightarrow2\left(x+5\right)-x\left(x+5\right)=0\Rightarrow\left(x+5\right)\left(2-x\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=-5\\x=2\end{matrix}\right.\)
e) \(\Rightarrow2x^2-10x-3x-2x^2=26\)
\(\Rightarrow-13x=26\Rightarrow x=-2\)
f) \(\Rightarrow\left(x-2012\right)\left(5x-1\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=2012\\x=\dfrac{1}{5}\end{matrix}\right.\)
a)
(2x-1)2-(5x-5)2=0
<=>(2x-1-5x+5)(2x-1+5x-5)=0
<=>(-3x+4)(7x-6)=0
<=>\(\orbr{\begin{cases}-3x+4=0\\7x-6=0\end{cases}}\)
<=>\(\orbr{\begin{cases}-3x=-4\\7x=6\end{cases}}\)
<=>\(\orbr{\begin{cases}x=\frac{-4}{-3}=\frac{4}{3}\\x=\frac{6}{7}\end{cases}}\)
b)
(2x+1)2-4(x+3)2=0
<=>(2x+1)2-[2(x+3)]2=0
<=>(2x+1)2-(2x+6)2=0
<=>(2x+1-2x-6)(2x+1+2x+6)=0
<=>-5(4x+7)=0
<=>4x+7=0
<=>4x=-7
<=>\(x=-\frac{7}{4}\)
Answer:
\(3x^2-4x=0\)
\(\Rightarrow x\left(3x-4\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x=0\\x=\frac{4}{3}\end{cases}}\)
\(\left(x^2-5x\right)+x-5=0\)
\(\Rightarrow x\left(x-5\right)+\left(x-5\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x-5=0\\x+1=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=5\\x=-1\end{cases}}\)
\(x^2-5x+6=0\)
\(\Rightarrow x^2-2x-3x+6=0\)
\(\Rightarrow\left(x^2-2x\right)-\left(3x-6\right)=0\)
\(\Rightarrow x\left(x-2\right)-3\left(x-2\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x-2=0\\x-3=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=2\\x=3\end{cases}}\)
\(5x\left(x-3\right)-x+3=0\)
\(\Rightarrow5x\left(x-3\right)-\left(x-3\right)=0\)
\(\Rightarrow\left(5x-1\right)\left(x-3\right)=0\)
\(\Rightarrow\orbr{\begin{cases}5x-1=0\\x-3=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=\frac{1}{5}\\x=3\end{cases}}\)
\(x^2-2x+5=0\)
\(\Rightarrow\left(x^2-2x+1\right)+4=0\)
\(\Rightarrow\left(x-1\right)^2=-4\) (Vô lý)
Vậy không có giá trị \(x\) thoả mãn
\(x^2+x-6=0\)
\(\Rightarrow x^2+3x-2x-6=0\)
\(\Rightarrow x.\left(x+3\right)-2\left(x+3\right)=0\)
\(\Rightarrow\left(x-2\right)\left(x+3\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x-2=0\\x+3=0\end{cases}\Rightarrow\orbr{\begin{cases}x=2\\x=-3\end{cases}}}\)
a) 5x(x - 1) = x - 1
5x(x - 1) - (x - 1) = 0
(x - 1) (5x - 1) = 0
TH1: x - 1 = 0
x = 1
TH2: 5x - 1 = 0
5x = 1
x = 1/5
Vay x = 1 hoac x = 1/5.
b) 2(x + 5) - x2 - 5x = 0
2(x + 5) - x(x + 5) = 0
(x + 5) (2 - x) = 0
TH1: x + 5 = 0
x = -5
TH2: 2 - x = 0
x = 2
Vay x = -5 hoac x = 2
\(\left(5x-1\right)\left(x-\frac{1}{3}\right)=0\)
\(\Rightarrow\orbr{\begin{cases}VP:5x-1=0\\VT:x-\frac{1}{3}=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=\frac{1}{5}\\x=\frac{1}{3}\end{cases}}\)
Vậy x của VP là 1/5 và x của VT là 1/3
(5x - 1).(x - 1/3) = 0
<=> \(\orbr{\begin{cases}5x-1=0\\x-\frac{1}{3}=0\end{cases}}\)
+) 5x -1 = 0 => x =1/5
+) x - 1/3 = 0 => x=1/3
Vậy x=1/5 , x=1/3
b) \(x\left(2x+5\right)=0\)
TH1: \(x=0\)
TH2: \(2x+5=0\Leftrightarrow2x=-5\Leftrightarrow x=\dfrac{-5}{2}\)
\(a,\Rightarrow5x\left(x-3\right)-\left(x-3\right)\left(x+3\right)=0\\ \Rightarrow\left(x-3\right)\left(5x-x-3\right)=0\\ \Rightarrow\left(x-3\right)\left(4x-3\right)=0\\ \Rightarrow\left[{}\begin{matrix}x=3\\x=\dfrac{3}{4}\end{matrix}\right.\\ b,\Rightarrow x\left(2x+5\right)=0\Rightarrow\left[{}\begin{matrix}x=0\\x=-\dfrac{5}{2}\end{matrix}\right.\)
\(a,\Leftrightarrow x\left(x+5\right)=0\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-5\end{matrix}\right.\\ b,\Leftrightarrow3x\left(x-1\right)+\left(x-1\right)=0\\ \Leftrightarrow\left(x-1\right)\left(3x+1\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=1\\x=-\dfrac{1}{3}\end{matrix}\right.\\ c,\Leftrightarrow\left(x+2\right)\left(2x-3\right)=0\Leftrightarrow\left[{}\begin{matrix}x=-2\\x=\dfrac{3}{2}\end{matrix}\right.\)
`3-1/5x=0`
`=> 1/5x=3-0`
`=> 1/5x=3`
`=> x= 3 : 1/5`
`=> x= 3 xx 5`
`=> x= 15`
3 - \(\dfrac{1}{5}\) \(x\) = 0
\(\dfrac{1}{5}x\) = 3
\(x\) = 3 : \(\dfrac{1}{5}\)
\(x\) = 15