$\begin{array}{l} 44)y' = 1 - \dfrac{1}{x},y' = 0 \Leftrightarrow x = 1 \notin \left[ {2;e} \right]\\  \Rightarrow f\left( 2 \right) = 2 - \ln 2,f\left( e \right) = e - 1\\  \Rightarrow \mathop {\min }\limits_{\left[ {2;e} \right]} f\left( x \right) = f\left( 2 \right) = 2 - \ln 2 \Rightarrow a = 2,b =  - 1\\  \Rightarrow a + b = 1 \to D\\ 45)y = f\left( {f\left( x \right)} \right)\\  \Rightarrow y' = f'\left( x \right)f'\left( {f\left( x \right)} \right)\\ y' = 0 \Leftrightarrow \left[ \begin{array}{l} f'\left( x \right) = 0\\ f'\left( {f\left( x \right)} \right) = 0 \end{array} \right.\\  \bullet f'\left( x \right) = 0 \Leftrightarrow \left[ \begin{array}{l} x =  - 2\\ x =  - 1\\ x = 0\\ x = 1\\ x = 3 \end{array} \right.\\  \bullet f'\left( {f\left( x \right)} \right) = 0 \Leftrightarrow \left[ \begin{array}{l} f\left( x \right) =  - 2 \to \left( {3{n_0}\, kép} \right)\\ f\left( x \right) =  - 1 \to \left( {4{n_0}\, đơn} \right)\\ f\left( x \right) = 0 \to \left( {4{n_0}\,đơn} \right)\\ f\left( x \right) = 1 \to \left( {4{n_0}\, đơn} \right)\\ f\left( x \right) = 3 \to \left( {2{n_o}\, đơn} \right) \end{array} \right.\\  \to \text{Số cực trị là}: 5 + 4 + 4 + 2 + 2 = 19ct \to D \end{array}$