Question

Giải phương trình:  x - \(\sqrt{x+1}\) = -1

Answer 1

\(\Leftrightarrow x+1=\sqrt{x+1}\)

\(\Leftrightarrow\left(x+1\right)^2=x+1\)

\(=>x+1=\dfrac{x+1}{x+1}=1\)

\(=>x=1-1=0\)

Answer 2

`x-\sqrt{x+1}=-1`             `ĐK: x >= -1`

`<=>x+1-\sqrt{x+1}=0`

`<=>(\sqrt{x+1})^2-\sqrt{x+1}=0`

`<=>\sqrt{x+1}(\sqrt{x+1}-1)=0`

`<=>` $\left[\begin{matrix} \sqrt{x+1}=0\\ \sqrt{x+1}=1\end{matrix}\right.$

`<=>` $\left[\begin{matrix} x+1=0\\ x+1=1\end{matrix}\right.$

`<=>` $\left[\begin{matrix} x=-1\\ x=0\end{matrix}\right.$  (t/m)

Vậy `S={-1;0}`