a) \(M=\left(2x-1\right)\left(2x+2\right)-\left(x-3\right)\left(x+3\right)\) \(=4x^2-2x+4x-2-\left(x^2-9\right)\)
\(=4x^2+2x-2-x^2+9\) \(=3x^2+2x+7\)
b) M = 11 \(\Leftrightarrow3x^2+2x+7=11\) \(\Leftrightarrow3x^2+2x-4=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{-1+\sqrt{13}}{3}\\x=\dfrac{-1-\sqrt{13}}{3}\end{matrix}\right.\)