Question

20x³-5x=0

Answer 1

20x³ - 5x =0

<=> x (20x² - 5 ) = 0

\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x^2=\frac{1}{4}\Rightarrow\left[{}\begin{matrix}x=\frac{1}{2}\\x=\frac{-1}{2}\end{matrix}\right.\end{matrix}\right.\)

Answer 2

20x³ - 5x = 0

<=> 5x(4x² - 1) = 0

<=> 5x(2x - 1)(2x + 1) = 0

<=> \(\left[{}\begin{matrix}5x=0\\2x-1=0\\2x+1=0\end{matrix}\right.\)

<=>\(\left[{}\begin{matrix}x=0\\x=\frac{1}{2}\\x=-\frac{1}{2}\end{matrix}\right.\)

Vậy phương trình có tập nghiệm là: \(S=\left\{0;\frac{1}{2};-\frac{1}{2}\right\}\)