Question

Tìm x thuộc Z biết:

a) (x-2)(x+4)=0

b) (x-3)(x-5)<0

Answer 1

a) \(\Rightarrow\orbr{\begin{cases}x-2=0\\x+4=0\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=2\\x=-4\end{cases}}\)

b) \(\Rightarrow\orbr{\begin{cases}x-3< 0\\x-5< 0\end{cases}}\)

\(\Rightarrow x\le0\)

Answer 2

a)x-2.x+4=0

  x.(-2+4)=0

  x.  2     =0

  x          =0:2

  x          =0

Answer 3

\(a,\left(x-2\right)\left(x+4\right)=0\Leftrightarrow\orbr{\begin{cases}x-2=0\\x+4=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=2\\x=-4\end{cases}}}\)

\(b,\left(x-3\right)\left(x-5\right)< 0\Leftrightarrow\hept{\begin{cases}x-3< 0\\x-5< 0\end{cases}}\Leftrightarrow\hept{\begin{cases}x< 3\\x< 5\end{cases}}\Leftrightarrow x< 5\)