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a,|x+1/2|=2/5
\(\Rightarrow\)\(\orbr{\begin{cases}\frac{x+1}{2}\\\frac{x+1}{2}\end{cases}}\)=+-2/5
x+1/2=2/5\(\Rightarrow\)x+1=4/5\(\Rightarrow\)x=9/5
x+1/2=-2/5\(\Rightarrow\)x+1=-4/5\(\Rightarrow\)x=1/5
Vậy x\(\in\){1/5;9/5}
Giải:
a) \(\dfrac{-5}{8}=\dfrac{x}{16}\)
\(\Rightarrow x=\dfrac{16.-5}{8}=-10\)
\(\dfrac{3x}{9}=\dfrac{2}{6}\)
\(\Rightarrow3x=\dfrac{2.9}{6}=3\)
\(\Rightarrow x=1\)
b) \(\dfrac{x+3}{15}=\dfrac{1}{3}\)
\(\Rightarrow x+3=\dfrac{1.15}{3}=5\)
\(\Rightarrow x=2\)
\(\dfrac{6}{2x+1}=\dfrac{2}{7}\)
\(\Rightarrow2x+1=\dfrac{6.7}{2}=21\)
\(\Rightarrow x=10\)
c) \(\dfrac{4}{x-6}=\dfrac{y}{24}=\dfrac{-12}{18}\)
\(\Rightarrow\dfrac{4}{x-6}=\dfrac{-12}{18}\)
\(\Rightarrow x-6=\dfrac{18.4}{-12}=-6\)
\(\Rightarrow x=0\)
\(\Rightarrow\dfrac{y}{24}=\dfrac{-12}{18}\)
\(\Rightarrow y=\dfrac{-12.24}{18}=-16\)
\(\dfrac{3-x}{-12}=\dfrac{16}{y+1}=\dfrac{192}{-72}\)
\(\Rightarrow\dfrac{3-x}{-12}=\dfrac{192}{-72}\)
\(\Rightarrow3-x=\dfrac{192.-12}{-72}=32\)
\(\Rightarrow x=-29\)
\(\Rightarrow\dfrac{16}{y+1}=\dfrac{192}{-72}\)
\(\Rightarrow y+1=\dfrac{16.-72}{192}=-6\)
d) \(\dfrac{-2}{3}< \dfrac{x}{5}< \dfrac{-1}{6}\)
\(\Rightarrow\dfrac{-20}{30}< \dfrac{6x}{30}< \dfrac{-5}{30}\)
\(\Rightarrow6x\in\left\{-18;-12;-6\right\}\)
\(\Rightarrow x\in\left\{-3;-2;-1\right\}\)
\(\dfrac{-1}{5}\le\dfrac{x}{8}\le\dfrac{1}{4}\)
\(\Rightarrow\dfrac{-8}{40}\le\dfrac{5x}{40}\le\dfrac{10}{40}\)
\(\Rightarrow5x\in\left\{-5;0;5;10\right\}\)
\(\Rightarrow x\in\left\{-1;0;1;2\right\}\)
e) \(\dfrac{x+46}{20}=x\dfrac{2}{5}\)
\(\Rightarrow\dfrac{x+46}{20}=x+\dfrac{2}{5}\)
\(\Rightarrow\dfrac{x+46}{20}=\dfrac{5x+2}{5}\)
\(\Rightarrow5.\left(x+46\right)=20.\left(5x+2\right)\)
\(\Rightarrow5x+230=100x+40\)
\(\Rightarrow5x-100x=40-230\)
\(\Rightarrow-95x=-190\)
\(\Rightarrow x=-190:-95\)
\(\Rightarrow x=2\)
\(y\dfrac{5}{y}=\dfrac{86}{y}\)
\(\Rightarrow y+\dfrac{5}{y}=\dfrac{86}{y}\)
\(\Rightarrow\dfrac{y^2+5}{y}=\dfrac{86}{y}\)
\(\Rightarrow y^2+5=86\)
\(\Rightarrow y^2=86-5\)
\(\Rightarrow y^2=81\)
\(\Rightarrow\left[{}\begin{matrix}y=9\\y=-9\end{matrix}\right.\)
Chúc bạn học tốt!
1.Tính
a) 7.[ 6 : 2 - 15 :(-3) - l-3l ]
= 7.[ 3 + 5 - 3]
= 7.[( 3 - 3 ) + 5]
= 7.[0 + 5]
= 7.5
= 35
b) 159.(18-59) - 59 .(18-159)
= 159 . ( - 41) - 59 . ( - 141 )
= ( - 6519 ) - ( - 8319 )
= 1800
2.Tìm x thuộc Z
a) x + 15 = 20 -4x
x+4x=20-15
5x=5
x=5:5
x=1
Vậy x=1
b) 3 - lx - 1l =0
|x-1|=3
* x-1=3 * x-1=-3
x=3+1 x=-3+1
x=4 x=-2
Vậy x=4 hoặc x=-2
c) 7(x-3) - 5 (3-x) = 11x - 5
7x-21-15+5x=11x-5
-21-15+5=11x-7x-5x
-31=-x
31=x
Vậy x=31
1) 2. I2x-3l = 1/2
|2x-3| =1/2:2
|2x-3| =1/4
=>2x-3 =1/4 hoặc 2x-3 =-1/4
2x =1/4+3 2x =-1/4+3
2x =13/4 2x =11/4
x =13/4:2 x =11/4:2
x =13/8 x =11/8
vậy x=13/8 hoặc 11/8
tich dung cho minh nhe
Bài 2:
a: =>x=0 hoặc x+3=0
=>x=0 hoặc x=-3
b: =>x-2=0 hoặc 5-x=0
=>x=2 hoặc x=5
c: =>x-1=0
hay x=1
Bài 2:
a: \(\left(6x-39\right):7=3\)
\(\Leftrightarrow6x-39=21\)
hay x=10
Bài 2 :
a, \(\left|x-\frac{5}{3}\right|< \frac{1}{3}\)
\(\Leftrightarrow\orbr{\begin{cases}x-\frac{5}{3}< \frac{1}{3}\\x-\frac{5}{3}< -\frac{1}{3}\end{cases}\Leftrightarrow\orbr{\begin{cases}x< 2\\x< \frac{4}{3}\end{cases}}}\)
b, \(\frac{2}{5}< \left|x-\frac{7}{5}\right|< \frac{3}{5}\)
\(\orbr{\begin{cases}\frac{2}{5}< x-\frac{7}{5}< \frac{3}{5}\\\frac{2}{5}< -x+\frac{7}{5}< \frac{3}{5}\end{cases}}\Leftrightarrow\orbr{\begin{cases}\frac{9}{5}< x< 2\\1>x>\frac{4}{5}\end{cases}}\)