Question

 

tìm x,biết

a) 3x² - 27x = 0

b) 2/3x ( x² - 4) = 0

Answer 1

\(3x^2-27x=0\)

\(3x\left(x-9\right)=0\)

\(\left[\begin{array}{nghiempt}x=0\\x-9=0\end{array}\right.\)

\(\left[\begin{array}{nghiempt}x=0\\x=9\end{array}\right.\)

\(\frac{2}{3}x\left(x^2-4\right)=0\)

\(\frac{2}{3}x\left(x-2\right)\left(x+2\right)=0\)

\(\left[\begin{array}{nghiempt}x=0\\x-2=0\\x+2=0\end{array}\right.\)

\(\left[\begin{array}{nghiempt}x=0\\x=2\\x=-2\end{array}\right.\)

Answer 2

a)\(3x^2-27x=0\)

\(3x\left(x-9\right)=0\)

\(\Rightarrow\left[\begin{array}{nghiempt}3x=0\\x-9=0\end{array}\right.\Rightarrow\left[\begin{array}{nghiempt}x=0\\x=9\end{array}\right.\)

b) \(\frac{2}{3}x\left(x^2-4\right)=0\)

\(\frac{2}{3}x\left(x+2\right)\left(x-2\right)=0\)

\(\Rightarrow\left[\begin{array}{nghiempt}\frac{2}{3}x=0\\x+2=0\\x-2=0\end{array}\right.\Rightarrow\left[\begin{array}{nghiempt}x=0\\x=-2\\x=2\end{array}\right.\)