Question

Tìm số hữu tỉ x, biết:

a) (x-1)⁵=-243

b) x-2\(\sqrt{x}\)=0 (x\(\ge\)0)

Answer 1

a) (x - 1)⁵ = -243

<=> (x - 1)⁵ = (-3)⁵

=> x - 1 = -3

=> x = -2

b) \(x-2\sqrt{x}=0\)

\(\sqrt{x^2}-2\sqrt{x}=0\)

\(\sqrt{x}.\left(\sqrt{x}-2\right)=0\)

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

Answer 2

a, \(\left(x-1\right)^5=-243\)

\(\Leftrightarrow x-1=-3\Leftrightarrow x=-2\)

Vậy x = -2

b, \(x-2\sqrt{x}=0\)

\(\Leftrightarrow\sqrt{x}\left(\sqrt{x}-2\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}\sqrt{x}=0\\\sqrt{x}-2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=\sqrt{2}\end{matrix}\right.\)

Vậy...