Question

TÌM X  biết :

c) x( x - 5 ) - 4x + 20 = 0

Answer 1

\(x\left(x-5\right)-4x+20=0\)

\(\Leftrightarrow x\left(x-5\right)-4\left(x-5\right)=0\)

\(\Leftrightarrow\left(x-5\right)\left(x-4\right)=0\)

\(\Leftrightarrow\left[\begin{array}{nghiempt}x-5=0\\x-4=0\end{array}\right.\)

\(\Leftrightarrow\left[\begin{array}{nghiempt}x=5\\x=4\end{array}\right.\)

Vậy \(x\in\left\{5;4\right\}\)

Answer 2

x(x-5)-4x+20=0

<=>x(x-5)-4(x-5)=0

=>(x-5)(x-4)=0

x-5=0

x-4=0

Vậy x thuộc tập hợp {5;4}