2 câu trả lời
$$\eqalign{ & \left( {x - 5} \right)\left( {x - 4} \right) - \left( {x + 1} \right)\left( {x - 2} \right) = 7 \cr & \Leftrightarrow {x^2} - 5x - 4x + 20 - {x^2} + 2x - x + 2 - 7 = 0 \cr & \Leftrightarrow - 8x + 15 = 0 \cr & \Leftrightarrow x = {{15} \over 8} \cr} $$