Question

\(^{x^2-3x-9=0}\)

Answer 1

Lời giải:
\(x^2-3x-9=0\)

\(\Leftrightarrow x^2-2.\frac{3}{2}x+(\frac{3}{2})^2-\frac{45}{4}=0\)

\(\Leftrightarrow (x-\frac{3}{2})^2=\frac{45}{4}\)

\(\Rightarrow \left[\begin{matrix} x-\frac{3}{2}=\frac{\sqrt{45}}{2}\\ x-\frac{3}{2}=-\frac{\sqrt{45}}{2}\end{matrix}\right.\Rightarrow \left[\begin{matrix} x=\frac{3}{2}+\frac{\sqrt{45}}{2}\\ x=\frac{3}{2}-\frac{\sqrt{45}}{2}\end{matrix}\right.\)