tìm x :
2,8:(3x-\(\frac{5}{8}\))=2\(\frac{2}{5}\)
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\(\Rightarrow\) 1/5-3x = 2/8 : 7/5 = 5/28
\(\Rightarrow\) 3x = 1/5 - 5/28 = 3/140
\(\Rightarrow\) x = 3/140 : 3 = 1/140
a) \(\left|2x\right|-\left|-2,5\right|=\left|-7,5\right|\)
\(\Leftrightarrow\left|2x\right|-2,5=7,5\)
\(\Leftrightarrow\left|2x\right|=10\)
\(\Leftrightarrow\begin{cases}x\ge0\\2x=10\end{cases}\) hoặc \(\begin{cases}x< 0\\2x=-10\end{cases}\)
\(\Leftrightarrow\begin{cases}x\ge0\\x=5\left(tm\right)\end{cases}\) hoặc \(\begin{cases}x< 0\\x=-5\left(tm\right)\end{cases}\)
Vậy x={5;-5}
b)\(\left|3x\right|\cdot\left|-3,5\right|=\left|-2,8\right|\)
\(\Leftrightarrow\left|3x\right|\cdot3,5=2,8\)
\(\Leftrightarrow\left|3x\right|=\frac{4}{5}\)
\(\Leftrightarrow\begin{cases}x\ge0\\3x=\frac{4}{5}\end{cases}\) hoặc \(\begin{cases}x< 0\\3x=-\frac{4}{5}\end{cases}\)
\(\Leftrightarrow\begin{cases}x\ge0\\x=\frac{4}{15}\end{cases}\) hoặc \(\begin{cases}x< 0\\x=-\frac{4}{15}\end{cases}\)
Vậy x={4/15;-4/15}
c) \(\left(3x-5\right)\left(\frac{3}{2}x+2\right)\left(0,5x-10\right)=0\)
\(\Leftrightarrow\left[\begin{array}{nghiempt}3x-5=0\\\frac{3}{2}x+2=0\\0,5x-10=0\end{array}\right.\)\(\Leftrightarrow\left[\begin{array}{nghiempt}x=\frac{5}{3}\\x=-\frac{4}{3}\\x=20\end{array}\right.\)
a)|2x|-|-2,5|=|-7,5|
|2x|-2,5=7,5
|2x|=10
\(\Rightarrow\left[\begin{array}{nghiempt}2x=10\\2x=-10\end{array}\right.\)\(\Rightarrow\left[\begin{array}{nghiempt}x=5\\x=-5\end{array}\right.\)
Vậy x=5;-5
\(2.8:\left(\frac{1}{5}-3x\right)=1\frac{2}{5}\)
\(\frac{14}{5}:\left(\frac{1}{5}-3x\right)=\frac{7}{5}\)
\(\frac{1}{5}-3x=\frac{14}{5}:\frac{7}{5}\)
\(\frac{1}{5}-3x=2\)
\(3x=\frac{1}{5}-2\)
\(3x=-\frac{9}{5}\)
\(x=-\frac{3}{5}\)
\(\frac{3x-7}{5}=\frac{2x-1}{3}\)
\(\Leftrightarrow9x-21=10x-5\)
\(\Leftrightarrow-x=16\Leftrightarrow x=-16\)
\(\frac{4x-7}{12}-x=\frac{3x}{8}\)
\(\Leftrightarrow\frac{4x-7-12x}{12}=\frac{3x}{8}\)
\(\Leftrightarrow\frac{-7-8x}{12}=\frac{3x}{8}\)
\(\Leftrightarrow-56-64x=36x\)
\(\Leftrightarrow-56=100x\Leftrightarrow x=\frac{-14}{25}\)
\(\frac{x-2009}{1234}+\frac{x-2009}{5678}-\frac{x-2009}{197}=0\)
\(\Leftrightarrow\left(x-2019\right)\left(\frac{1}{1234}+\frac{1}{5678}-\frac{1}{197}\right)=0\)
Vì \(\left(\frac{1}{1234}+\frac{1}{5678}-\frac{1}{197}\right)\ne0\)nên x - 2019 = 0
Vậy x = 2019
\(\frac{5x-8}{3}=\frac{1-3x}{2}\)
\(\Leftrightarrow10x-16=3-9x\)
\(\Leftrightarrow19x=19\Leftrightarrow x=1\)
\(\frac{3x+5}{2}+\frac{3x+5}{4}+\frac{3x+5}{6}=\frac{3x+5}{8}\)
\(\frac{3x+5}{2}+\frac{3x+5}{4}+\frac{3x+5}{6}-\frac{3x+5}{8}=0\)
\(\left(3x-5\right)\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{6}-\frac{1}{8}\right)=0\)
\(\Rightarrow x=-\frac{5}{3}\)
\(\frac{3x+2}{2x^2-x-15}=\frac{3x-8}{2x^2+4x-20}\)
=>(3x+2)(2x2+4x-20)=(3x-8)(2x2-x-15)
=>6x3+16x2-52x-40=6x3-19x2-37x+120
=>16x2-52x-40=-19x2-37x+120
=>35x2=15x+160
=>7x2=3x+32
=>7x2-3x-32=0
\(\Rightarrow\left(\sqrt{7}x\right)^2-2\sqrt{7}x.\frac{3\sqrt{7}}{14}+\frac{9}{28}-\frac{905}{28}=0\)
\(\Rightarrow\left(\sqrt{7}x-\frac{3\sqrt{7}}{14}\right)^2=\frac{905}{28}\)
từ đó tìm x
a) Qui đồng rồi khử mẫu ta được:
3(3x+2)-(3x+1)=2x.6+5.2
<=> 9x+6-3x-1 = 12x+10
<=> 9x-3x-12x = 10-6+1
<=> -6x = 5
<=> x = -5/6
Vậy ....
b) ĐKXĐ: \(x\ne\pm2\)
Qui đồng rồi khử mẫu ta được:
(x+1)(x+2)+(x-1)(x-2) = 2(x2+2)
<=> x2+3x+2+x2-3x+2 = 2x2+4
<=> x2+x2-2x2+3x-3x = 4-2-2
<=> 0x = 0
<=> x vô số nghiệm
Vậy x vô số nghiệm với x khác 2 và x khác -2
c) \(\left(2x+3\right)\left(\frac{3x+7}{2-7x}+1\right)=\left(x-5\right)\left(\frac{3x+8}{2-7x}+1\right)\) (ĐKXĐ:x khắc 2/7)
\(\Leftrightarrow\left(2x+3\right)\left(\frac{3x+8}{2-7x}+1\right)-\left(x-5\right)\left(\frac{3x+8}{2-7x}+1\right)=0\)
\(\Leftrightarrow\left(\frac{3x+8}{2-7x}+1\right)\left[\left(2x+3\right)-\left(x-5\right)\right]=0\)
\(\Leftrightarrow\left(\frac{3x+8}{2-7x}+1\right)\left(x+8\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}\frac{3x+8}{2-7x}+1=0\\x+8=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}\frac{3x+8}{2-7x}=-1\\x+8=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}3x+8=-1\left(2-7x\right)\\x=0-8\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}3x+8=-2+7x\\x=-8\end{cases}\Leftrightarrow\orbr{\begin{cases}-4x=-10\\x=-8\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=\frac{5}{2}\\x=-8\end{cases}}}\) (nhận)
Vậy ......
d) (x+1)2-4(x2-2x+1) = 0
<=> x2+2x+1-4x2+8x-4 = 0
<=> -3x2+10x-3 = 0
giải phương trình
a)x+3/6=7/2
x =7/2-3/6
x =3
b)2,8+(3x-5/6)=2/2/5
14/5+(3x-5/6)=12/5
(3x-5/6)=12/5-14/5
3x+5/6=-2/5
3x =-2/5-5/6
3x =-37/30
x =-37/36:3
x =-37/90
\(2,8:\left(3.x-\frac{5}{8}\right)=2\frac{2}{5}\)
=>\(\frac{14}{5}:\left(3.x-\frac{5}{8}\right)=\frac{12}{5}\)
=>\(\frac{14}{5}:\frac{13}{5}=3.x-\frac{5}{8}\)
=>\(3.x-\frac{5}{8}=\frac{14}{13}\)
=>\(3.x=\frac{14}{13}+\frac{5}{8}\)
=>\(3.x=\frac{177}{104}\)
=>\(x=\frac{59}{104}\)
2,8 :( 3x -5/8)= 2/2/5
2,8:( 3x- 5,8)= 12/5
3x-5/8 = 2,8:12/5
3x -5/8 = 7/6
3x= 7/6 +5/8
3x= 43/ 24
x= 43/24 :3
x= 43/72
nha bn, mknghix vậy