(x-2phan5) nhan 1phan2 =1
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\(a,\dfrac{11}{12}-\left(\dfrac{2}{5}+x\right)=\dfrac{2}{3}\)
\(\dfrac{2}{5}+x=\dfrac{11}{12}-\dfrac{2}{3}\)
\(\dfrac{2}{5}+x=\dfrac{1}{4}\)
\(x=\dfrac{1}{4}-\dfrac{2}{5}\)
\(x=\dfrac{-3}{20}\)
Vậy ...
b, \(2x\left(x-\dfrac{1}{7}\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}2x=0\\x-\dfrac{1}{7}=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=\dfrac{1}{7}\end{matrix}\right.\)
Vậy ...
c, \(\dfrac{3}{4}+\dfrac{1}{4}:x=\dfrac{2}{5}\)
\(\dfrac{1}{4}:x=\dfrac{2}{5}-\dfrac{3}{4}\)
\(\dfrac{1}{4}:x=\dfrac{-7}{20}\)
\(x=\dfrac{1}{4}:\dfrac{-7}{20}\)
\(x=\dfrac{-5}{7}\)
Vậy ...
a)\(\dfrac{11}{12}-\left(\dfrac{2}{5}+x\right)=\dfrac{2}{3}\)
<=>\(\dfrac{2}{5}+x=\dfrac{1}{4}\)
<=>\(x=\dfrac{1}{4}-\dfrac{2}{5}\)
<=>\(x=-\dfrac{3}{20}\)
b)\(2x\left(x-\dfrac{1}{7}\right)=0\)
=>\(\text{2x=0 hoặc }x-\dfrac{1}{7}=0\)
=>\(x=0hoặcx=\dfrac{1}{7}\)
Vậy....
c)\(\dfrac{3}{4}+\dfrac{1}{4}:x=\dfrac{2}{5}\)
=>\(\dfrac{1}{4}:x=-\dfrac{7}{20}\)
=>x=\(-\dfrac{5}{7}\)
Vậy
25%.x+1/2.x=12
=> 1/4.x+1/2.x=12
=> x.(1/4+1/2)=12
=> x.0,75 =12
=> x =12:0,75
=> x =16
Vậy x=16
25/100.x + 1/2.x = 12
1/10.x + 1/2.x =12
(1/10 + 1/2 ).x =12
( 1/10 + 5/10 ).x =12
6/10 = 3/5.x = 12
x = 12 : 3/5
x = 12 . 5/3
x = 20
\(a\times\frac{1}{2}=\frac{a}{2}\)
Vì số nào nhân với 1 cũng bằng chính số đó thôi
\(\frac{25-x}{18}=\frac{1}{2}\)
\(\frac{25-x}{18}=\frac{9}{18}\)
\(25-x=9\)
\(x=25-9\)
\(x=16\)
\(\left(x-\frac{2}{5}\right)×\frac{1}{2}=1=>\left(x-\frac{2}{5}\right)=1:\frac{1}{2}=>\left(x-\frac{2}{5}\right)=2=>x=2+\frac{2}{5}=>x=\frac{12}{5}\)
vậy \(x=\frac{12}{5}\)
Bài làm :
Ta có :
\(\left(x-\frac{2}{5}\right)\times\frac{1}{2}=1\)
\(x-\frac{2}{5}=1\div\frac{1}{2}\)
\(x-\frac{2}{5}=2\)
\(x=2+\frac{2}{5}=2,4\)
Vậy x=2,4