a, \(A=\dfrac{x^2-12x+36}{2x^2-72}\)
\(\Leftrightarrow A=\dfrac{\left(x-6\right)^2}{2\left(x^2-36\right)}\)
\(\Leftrightarrow A=\dfrac{\left(x-6\right)^2}{2\left(x-6\right)\left(x+6\right)}\)
\(\Leftrightarrow A=\dfrac{x-6}{2\left(x+6\right)}\)
b, \(A=-\dfrac{3}{2}\) rồi mà bạn