Tất cả các bài kiểm tra điều kiện sau cùng:
$\begin{array}{l} 33)\sqrt {{x^2} - 5x + 4} = 2\\ \Leftrightarrow {x^2} - 5x + 4 = 4 \Leftrightarrow {x^2} - 5x = 0\\ \Leftrightarrow x\left( {x - 5} \right) = 0\\ \Leftrightarrow \left[ \begin{array}{l} x = 0\\ x = 5 \end{array} \right.(TM) \Rightarrow S = \left\{ {0;5} \right\}\\ 34)\sqrt {2{x^2} - 4x + 6} = 2\\ \Leftrightarrow 2{x^2} - 4x + 6 = 4 \Leftrightarrow 2{x^2} - 4x + 2 = 0\\ \Leftrightarrow {x^2} - 2x + 1 = 0\\ \Leftrightarrow {\left( {x - 1} \right)^2} = 0 \Leftrightarrow x = 1(TM) \Rightarrow S = \left\{ 1 \right\}\\ 35)\sqrt {{x^2} - 7x + 1} = 3\\ \Leftrightarrow {x^2} - 7x + 1 = 9 \Leftrightarrow {x^2} - 7x - 8 = 0\\ \Leftrightarrow \left( {x + 1} \right)\left( {x - 8} \right) = 0\\ \Leftrightarrow \left[ \begin{array}{l} x = - 1\\ x = 8 \end{array} \right.(TM) \Rightarrow S = \left\{ { - 1;8} \right\}\\ 36)\sqrt {3{x^2} - 4x + 5} = 2\\ \Leftrightarrow 3{x^2} - 4x + 5 = 4 \Leftrightarrow 3{x^2} - 4x + 1 = 0\\ \Leftrightarrow \left( {x - 1} \right)\left( {3x - 1} \right) = 0\\ \Leftrightarrow \left[ \begin{array}{l} x = 1\\ x = \dfrac{1}{3} \end{array} \right.(TM) \Rightarrow S = \left\{ {1;\dfrac{1}{3}} \right\} \end{array}$
