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-->2x:4+80:4=x+1
-->0,5x+20=x+1
-->20-1=x-0,5x
-->19=0,5x
-->x=19:0,5=38
_______________________
li-ke cho mk nha bn lam quoc phong
a/
$(2x-3\frac{1}{2})+250\text{%}=6,2$
$(2x-\frac{7}{2})+2,5=6,2$
$2x-\frac{7}{2}=6,2-2,5=3,7$
$2x=3,7+\frac{7}{2}=7,2$
$x=7,2:2=3,6$
b/
$(25\text{%}-4\frac{1}{2}x)-2\frac{1}{2}.4^2=5,25$
$(0,25-\frac{9}{2}x)-40=5,25$
$0,25-\frac{9}{2}x=45,25$
$\frac{9}{2}x=0,25-45,25=-45$
$x=-45:\frac{9}{2}=-10$
a: 3^x=243
=>3^x=3^5
=>x=5
b: 4^x=4096
=>4^x=4^5
=>x=5
c: 5^3-x=25
=>3-x=2
=>x=1
d: =>2x-3=3
=>2x=6
=>x=3
j: =>2^x*8+2^x*2=80
=>2^x=8
=>x=3
Giải:
a) \(\dfrac{12}{16}=\dfrac{-x}{4}=\dfrac{21}{y}=\dfrac{z}{80}\)
\(\Rightarrow x=\dfrac{12.-4}{16}=-3\)
\(\Rightarrow y=\dfrac{16.21}{12}=28\)
\(\Rightarrow z=\dfrac{12.80}{16}=60\)
b) \(\dfrac{1}{3}x+\dfrac{2}{5}\left(x-1\right)\) =0
\(\dfrac{1}{3}x+\dfrac{2}{5}x-\dfrac{2}{5}=0\)
\(x.\left(\dfrac{1}{3}+\dfrac{2}{5}\right)\) \(=0+\dfrac{2}{5}\)
\(x.\dfrac{11}{15}\) \(=\dfrac{2}{5}\)
x \(=\dfrac{2}{5}:\dfrac{11}{15}\)
x \(=\dfrac{6}{11}\)
c) (2x-3)(6-2x)=0
⇒2x-3=0 hoặc 6-2x=0
x=3/2 hoặc x=3
d) \(\dfrac{-2}{3}-\dfrac{1}{3}\left(2x-5\right)=\dfrac{3}{2}\)
\(\dfrac{1}{3}\left(2x-5\right)=\dfrac{-2}{3}-\dfrac{3}{2}\)
\(\dfrac{1}{3}\left(2x-5\right)=\dfrac{-13}{6}\)
\(2x-5=\dfrac{-13}{6}:\dfrac{1}{3}\)
\(2x-5=\dfrac{-13}{2}\)
\(2x=\dfrac{-13}{2}+5\)
\(2x=\dfrac{-3}{2}\)
\(x=\dfrac{-3}{2}:2\)
\(x=\dfrac{-3}{4}\)
e) \(2\left|\dfrac{1}{2}x-\dfrac{1}{3}\right|=\dfrac{1}{4}\)
\(\left|\dfrac{1}{2}x-\dfrac{1}{3}\right|=\dfrac{1}{4}:2\)
\(\left|\dfrac{1}{2}x-\dfrac{1}{3}\right|=\dfrac{1}{8}\)
\(\Rightarrow\dfrac{1}{2}x-\dfrac{1}{3}=\dfrac{1}{8}\) hoặc \(\dfrac{1}{2}x-\dfrac{1}{3}=\dfrac{-1}{8}\)
\(x=\dfrac{11}{12}\) hoặc \(x=\dfrac{5}{12}\)
a) 4.(x + 2) = 2 .(x - 1) + 4
=> 4x + 8 = 2x - 2 + 4
=> 4x + 8 = 2x + 2
=> 4x - 2x = 2 - 8
=> 2x = -6
=> x = -3
b) (x + 1) + ( 2x + 2) + (3x + 3) + ( 4x + 4) = 80
=> (x + 2x + 3x + 4x ) + (1 + 2 + 3 + 4) = 80
=> 10x + 10 = 80
=> 10x = 70
=> x = 7
a, 4.(x+2) = 2.(x-1) +4
4x +8 = 2x-2+4
4x-2x =-2+4-8
2x = -6
x = -3
b, (x+1)+(2x+2)+ ( 3x+3) + ( 4x+4) =80
(x+1)+ 2 .(x+1) +3. (x+1) +4. (x+1) =80
(1+2+3+4) (x+1)=80
10.(x+1) =80
x+1 =8
x=7
Tìm x:
b) 1/3.x+2/5.(x-1)=0
\(<=> \dfrac{1}{3} .x +\dfrac{2}{5}x - \dfrac{2}{5} =0\)
\(<=> \dfrac{11}{15}x = \dfrac{2}{5}\)
\(<=> x= \dfrac{6}{11}\)
Vậy \( x= \dfrac{6}{11}\)
c) (2x-3).(6-2x)=0
\(<=> \begin{cases}
2x-3=0 \\
6-2x=0
\end{cases}\) \(<=> \begin{cases}
2x=3 \\
-2x=-6
\end{cases}\) \(<=>\begin{cases}
x=\dfrac{3}{2} \\
x=3
\end{cases}\)
Vậy \(x=( \dfrac{3}{2} ; 3)\)
d) -2/3-1/3.(2x-5)= 3/2
\(<=> 2x-5= \dfrac{5}{2}\)
\(<=> 2x= \dfrac{15}{2}\)
\(<=> x= \dfrac{15}{4}\)
Vậy \(x= \dfrac{15}{4}\)
f) 1/3.x-1/2=4 và 1/2 (Hỗn số ý '^')
\(<=> \dfrac{1}{3} x -\dfrac{1}{2} = \dfrac{9}{2}\)
\(<=> \dfrac{1}{3}x =5\)
\(<=> x= 15\)
Vậy \(x= 15\)