Question

Giải phương trình : \(\sqrt{x^2-4}=x-2\)

Answer 1

\(\sqrt{x^2-4}=x-2\)

\(\Leftrightarrow\left(\sqrt{x^2-4}\right)^2=\left(x-2\right)^2\)

\(\Leftrightarrow x^2-4=x^2-4+4\)

<=> x = 2

Answer 2

Ta có

\(\sqrt{x^2-4}=x-2\Leftrightarrow\left(x+2\right)\left(x-2\right)=\left(x-2\right)^2\)

\(\Leftrightarrow x+2=x-2\Rightarrow PT\) vô nghiệm