a) \(\left(x-2\right)\left(x+4\right)=0\)
\(\Rightarrow\left[\begin{array}{nghiempt}x-2=0\\x+4=0\end{array}\right.\) \(\Rightarrow\left[\begin{array}{nghiempt}x=0+2\\x=0-4\end{array}\right.\)
\(\Rightarrow\left[\begin{array}{nghiempt}x=2\\x=-4\end{array}\right.\)
Vậy: \(x\in\left\{2;-4\right\}\)
b) \(\left(x-2\right)\left(x+15\right)=0\)
\(\Rightarrow\begin{cases}x-2=0\\x+15=0\end{cases}\)
\(\Rightarrow\left[\begin{array}{nghiempt}x=0+2\\x=0-15\end{array}\right.\)
\(\Rightarrow\left[\begin{array}{nghiempt}x=2\\x=-15\end{array}\right.\)
Vậy: \(x\in\left\{2;-15\right\}\)
c) \(\left(x-3\right)\left(x-5\right)< 0\)
\(\Rightarrow\left[\begin{array}{nghiempt}x-3< 0\\x-5< 0\end{array}\right.\) \(\Rightarrow\left[\begin{array}{nghiempt}x< 0+3\\x< 0+5\end{array}\right.\)
\(\Rightarrow\left[\begin{array}{nghiempt}x< 3\\x< 5\end{array}\right.\) \(\Rightarrow3< x< 5\)
Vậy: \(x\in\left\{4\right\}\)
a) \(\left(x-2\right).\left(x+4\right)=0\)
\(\Rightarrow\begin{cases}x-2=0\\x+4=0\end{cases}\)
\(\Rightarrow\begin{cases}x=0+2\\x=0-4\end{cases}\)
\(\Rightarrow\begin{cases}x=2\\x=-4\end{cases}\)
Vậy x thuộc { 2 ; - 4 }
b) \(\left(x-2\right).\left(x+15\right)=0\)
\(\Rightarrow\begin{cases}x-2=0\\x+15=0\end{cases}\)
\(\Rightarrow\begin{cases}x=0+2\\x=0-15\end{cases}\)
\(\Rightarrow\begin{cases}x=2\\x=-15\end{cases}\)
Vậy x thuộc { 2 ; - 15 }
c) \(\left(x-3\right).\left(x-5\right)< 0\)
=> \(x-3\) và \(x-5\) trái dấu
Mà \(x-3>x-5\Rightarrow x-3>0\) và \(x-5< 0\)
\(\Rightarrow\begin{cases}x-3>0\Rightarrow x>3\\x-5< 0\Rightarrow x< 5\end{cases}\)
=> \(3< x< 5\)
=> \(x=4\)
Vậy x = 4
a) (x - 2 ) . ( x + 4 ) = 0
\(x-2=0\)hoặc\(x+4=0\)
\(x=2\)hoặc\(x=-4\)
b) (x - 2 ) . ( x + 15 ) = 0
x - 2 = 0 hoặc x + 15 = 0
x = 2 hoặc x = -15
c) ( x - 3 ) . ( x - 5 ) < 0
\(\begin{cases}x-3>0\\x-5< 0\end{cases}\Rightarrow\begin{cases}x>3\\x< 5\end{cases}\Rightarrow}3< x< 5}\)
Vậy x = 4
a) (x - 2 ) . ( x + 4 ) = 0
x−2=0x−2=0hoặcx+4=0x+4=0
x=2x=2hoặcx=−4x=−4
b) (x - 2 ) . ( x + 15 ) = 0
x - 2 = 0 hoặc x + 15 = 0
x = 2 hoặc x = -15
c) ( x - 3 ) . ( x - 5 ) < 0
\(x-3>0\) \(x>3\)
\(\Rightarrow\) \(\Rightarrow3< x< 5\)
\(x-5< 0\) \(x< 5\)
Vậy x = 4
