a)(x-2)(x+4)=0
<=>x-2=0 hoặc x+4=0
<=>x=2 hoặc x=-4
Vậy S={2;-4}
b)(x-3)(x-5)<0
<=>\(\left\{{}\begin{matrix}x-3< 0\\x-5>0\end{matrix}\right.\)hoặc\(\left\{{}\begin{matrix}x-3>0\\x-5< 0\end{matrix}\right.\)
<=>\(\left\{{}\begin{matrix}x< 3\\x>5\end{matrix}\right.\)(vô lí) hoặc \(\left\{{}\begin{matrix}x>3\\x< 5\end{matrix}\right.\)
<=>3<x<5
Vậy...
nay ban Trinh oi! ban lam qua dung roi do . tui cho ban 1 like
a) ( x - 2 ) . ( x + 4 ) = 0
=> Ta có hai trường hợp
TH1: x - 2 = 0
x = 0 + 2
x = 2
TH2: x + 4 = 0
x = 0 - 4
x = -4
Vậy x = 2 và x = -4
Lời giải:
a, \(\left(x-2\right)\left(x+4\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x-2=0\\x+4=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=2\\x=-4\end{matrix}\right.\)
b, \(\left(x-3\right)\left(x-5\right)< 0\)
\(\Rightarrow\left\{{}\begin{matrix}x-3< 0\\x-5< 0\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x< 0+3\\x< 0+5\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x< 3\\x< 5\end{matrix}\right.\)
