100x = -100 + 120x

=> -100 = -20x

=> x = 5

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

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

b)\(x^2-3x+2=0\Rightarrow\left(x-2\right)\left(x-1\right)=0\)

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

d)truong hop 1: voi x>0 <=> x-7=7-x<=>x+x=7+7<=>2x=14<=>x=7

  truong hop 2: voi x<0 <=.> 7-x=7-x k co gtri 

cac phan sau tuong tu nhe!

x=-2013

tick nhé!

2013 mk chắc như đinh đóng cột lun 

nhớ tick nha

s=2014+2013+..+x

=(2014)+2013+2012+...+x

s=2014

=> 2013+2012+..+x=0

hai số nguyên đối nhau có tổng =0 =>x=-2013

1.2(x-1)+(x-2)=x-4

         2x-2+x-2=x-4

            2x+ x-x=2+2-4

                    2x=0

=>                  x=0

Vậy x=0

`x/2=2/x`

`=>x.x=2.2`

`=>x^2=4`

`=>x=+-2`

vì (2x-1)^2014 + (y-2/5)^2014 + /x+y-z/=0

(2x-1)^2014=0

((y-2/5)^2014=0

/x+y+z/=0

vậy 2x-1=0 thì x=1/2

y-2/5=0 thì y=2/5

x+y+z=0=1/2 +2/5 +z=0 thi z=-9/10

mk mới học lớp 5 thôi