Question

tìm x , biết :

a) \(x^3\)-0,25x=0

b) \(x^2\)-10x=-25

Answer 1

a) \(x^3-0,25x=0\)

\(\Rightarrow x^3=\dfrac{1}{4}x\)

\(\Rightarrow x^2=\dfrac{1}{4}\)

\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{1}{2}\\x=-\dfrac{1}{2}\end{matrix}\right.\)

b) \(x^2-10x=-25\)

\(\Rightarrow x^2=-25+10x\)

\(\Rightarrow\left[{}\begin{matrix}x=-25+10x\\x=-\left(-25+10x\right)\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}10x-x=-25\\-10x-x=25\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}9x=-25\\-11x=25\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{-25}{9}\\x=-\dfrac{25}{11}\end{matrix}\right.\)