tim x ho minh nhe
2x -1.2x + 4.2x=9.2^5
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2
17 tháng 9 2016
Vì \(\left|x-\frac{2}{5}\right|\ge0;\left|2y+3\right|\ge0;\left(z-2\right)^2\ge0\)
=> \(\left|x-\frac{2}{5}\right|+\left|2y+3\right|+\left(z-2\right)^2\ge0\)
Mà theo đề bài: \(\left|x-\frac{2}{5}\right|+\left|2y+3\right|+\left(z-2\right)^2=0\)
=> \(\begin{cases}\left|x-\frac{2}{5}\right|=0\\\left|2y+3\right|=0\\\left(z-2\right)^2=0\end{cases}\)=> \(\begin{cases}x-\frac{2}{5}=0\\2y+3=0\\z-2=0\end{cases}\)=> \(\begin{cases}x=\frac{2}{5}\\2y=-3\\z=2\end{cases}\)=> \(\begin{cases}x=\frac{2}{5}\\y=-\frac{3}{2}\\z=2\end{cases}\)
Vậy \(x=\frac{2}{5};y=-\frac{3}{2};z=2\)
IM
17 tháng 9 2016
Ta có :
\(\left|x-\frac{2}{5}\right|+\left|2y+3\right|+\left(z-2\right)^2=0\)
Vì \(\begin{cases}\left|x-\frac{2}{5}\right|\ge0\\\left|2y+3\right|\ge0\\\left(z-2\right)^2\ge0\end{cases}\)\(\Rightarrow\begin{cases}x-\frac{2}{5}=0\\2y+3=0\\z-2=0\end{cases}\)\(\Rightarrow\begin{cases}x=\frac{2}{5}\\2y=-\frac{3}{2}\\z=2\end{cases}\)
Vậy .................
MN
0
PT
1
CM
25 tháng 6 2017
4.2x – 3 = 125
4.2x = 125 + 3
4.2x = 128
2x = 128 : 4
2x = 32
2x = 25
x = 5
Vậy x = 5
28 tháng 1 2022
\(1,\) thiếu đề
\(2,\dfrac{5x+2}{6}-\dfrac{8x-1}{3}=\dfrac{4x+2}{5}-5\)
\(\Leftrightarrow\dfrac{5\left(5x+2\right)}{30}-\dfrac{10\left(8x-1\right)}{30}=\dfrac{6\left(4x+2\right)}{30}-\dfrac{150}{30}\)
\(\Leftrightarrow5\left(5x+2\right)-10\left(8x-1\right)=6\left(4x+2\right)-150\)
\(\Leftrightarrow25x+10-80x+10=24x+12-150\)
\(\Leftrightarrow-55x+20=24x-138\)
\(\Leftrightarrow24x-138+55x-20=0\)
\(\Leftrightarrow79x-158=0\)
\(\Leftrightarrow x=2\)
\(3,ĐKXĐ:\left\{{}\begin{matrix}x\ne1\\x\ne-1\\x\ne3\end{matrix}\right.\\ \dfrac{x}{2x-6}+\dfrac{x}{2x-2}=\dfrac{-2x}{\left(x+1\right)\left(3-x\right)}\)
\(\Leftrightarrow\dfrac{x}{2\left(x-3\right)}+\dfrac{x}{2\left(x-1\right)}+\dfrac{2x}{\left(x+1\right)\left(3-x\right)}=0\)
\(\Leftrightarrow\dfrac{x}{2\left(x-3\right)}+\dfrac{x}{2\left(x-1\right)}-\dfrac{2x}{\left(x+1\right)\left(x-3\right)}=0\)
\(\Leftrightarrow x\left(\dfrac{1}{2\left(x-3\right)}+\dfrac{1}{2\left(x-1\right)}-\dfrac{2}{\left(x+1\right)\left(x-3\right)}\right)=0\)
\(\Leftrightarrow x\left(\dfrac{\left(x-1\right)\left(x+1\right)}{2\left(x-1\right)\left(x-3\right)\left(x+1\right)}+\dfrac{\left(x-3\right)\left(x+1\right)}{2\left(x-1\right)\left(x-3\right)\left(x+1\right)}-\dfrac{4\left(x-1\right)}{2\left(x+1\right)\left(x-3\right)\left(x-1\right)}\right)=0\)
\(\Leftrightarrow x\left(\dfrac{x^2-1}{2\left(x-1\right)\left(x-3\right)\left(x+1\right)}+\dfrac{x^2-2x-3}{2\left(x-1\right)\left(x-3\right)\left(x+1\right)}-\dfrac{4x-4}{2\left(x+1\right)\left(x-3\right)\left(x-1\right)}\right)=0\)
\(\Leftrightarrow x.\dfrac{x^2-1+x^2-2x-3-4x+4}{2\left(x-1\right)\left(x-3\right)\left(x+1\right)}=0\)
\(\Leftrightarrow x.\dfrac{2x^2-6x}{2\left(x-1\right)\left(x-3\right)\left(x+1\right)}=0\)
\(\Leftrightarrow x.\dfrac{2x\left(x-3\right)}{2\left(x-1\right)\left(x-3\right)\left(x+1\right)}=0\)
\(\Leftrightarrow x.\dfrac{x}{\left(x-1\right)\left(x+1\right)}=0\)
\(\Leftrightarrow\dfrac{x^2}{\left(x-1\right)\left(x+1\right)}=0\)
\(\Leftrightarrow x=0\)
29 tháng 7 2017
\(x^2+3x+2\) =\(x^2+2.\frac{3}{2}x+\left(\frac{3}{2}\right)^2-\frac{5}{4}\)=\(\left(x+\frac{3}{2}\right)^2-\frac{5}{4}\ge-\frac{5}{4}\)
Dấu "=" xảy ra <=>\(x+\frac{3}{2}=0\)<=>\(x=-\frac{3}{2}\)
Bài 2:
a) \(x^2-4x+y^2+2y+5=0\)
=> \(\left(x^2-4x+4\right)+\left(y^2+2y+1\right)=0\)
=>\(\left(x-2\right)^2+\left(y+1\right)^2=0\)
Vì \(\left(x-2\right)^2+\left(y+1\right)^2\ge0\)nên:
=>\(\hept{\begin{cases}x-2=0\\y+1=0\end{cases}}\)<=>\(\hept{\begin{cases}x=2\\y=-1\end{cases}}\)
b)\(2x^2+y^2-2xy+10x+25=0\)
=>\(\left(x^2-2xy+y^2\right)+\left(x^2+10x+25\right)=0\)
=>\(\left(x-y\right)^2+\left(x+5\right)^2=0\)
Tới đây thì dễ nhá !
21 tháng 11 2016
<=>(1.2x)^3=(-2)^3
<=>1.2x=-2
<=>2x=-2
<=>x=-2:2
<=>x=-1
Vậy x=-1
<3 <3