`a, 2x+5=0`

`=> 2x=-5`

`=>x=-5/2`

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`(5x+1)(2x-3)=0`

\(\Rightarrow\left[{}\begin{matrix}5x+1=0\\2x-3=0\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}5x=-1\\2x=3\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{1}{5}\\x=\dfrac{3}{2}\end{matrix}\right.\)

__

`0,5 x +1=0`

`=>0,5x=-1`

`=> x=-1/(0,5)`

`=>x= -2`

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`4x^2+7x=0`

`=> x(4x+7)=0`

\(\Rightarrow\left[{}\begin{matrix}x=0\\4x+7=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=0\\x=-\dfrac{7}{4}\end{matrix}\right.\)

`1/2 : 1/3 : 1/4`

`= 1/2 xx 3 xx 4`

`= 12/2`

`=6`

`1/3 xx 4/5 + 1/3 xx 6/5 - 1/3`

`=1/3 xx 4/5 + 1/3 xx 6/5 - 1/3xx1`

`= 1/3 xx ( 4/5 + 6/5 -1)`

`= 1/3 xx 1`

`=1/3`

=13 giờ 36 phút

   1 giờ 32 phút

+ 12 giờ 4 phút 

   --------------------

   13 giờ 36 phút

`1/3 xx 1/4 + 1/3 xx 6/5 - 1/3`

`=1/3 xx 1/4 + 1/3 xx 6/5 - 1/3xx1`

`=1/3 xx (1/4 + 6/5 -1)`

`=1/3xx 9/20`

`= 9/60`

`= 3/20`

`-4/5 + 2x =1/3 -2/3x`

`=>  2x + 2/3x =1/3 +4/5`

`=> (2 +2/3) x= 5/15 + 12/15`

`=> ( 6/3 +2/3) x= 17/15`

`=> 8/3 x= 17/15`

`=> x= 17/15 : 8/3`

`=> x= 17/15 xx 3/8`

`=>x=17/40`

` @ ` \(yeuugialinhh\)

`1/2 m^2 =1/2 xx 10000= 5000cm^2`

`0,008m^3 = 0,008  xx1000=8dm^3`

`1/5km=25...` ( mình thấy ko có cái gì cả )

`0,87 kg=0,87 xx1000=870g`

`@ `\(yGLinh\)