Đáp án:
Giải thích các bước giải:
\(\begin{array}{l}
DK:x \ne \left\{ {8;9;10;11} \right\}\\
Pt \to 8\left( {x - 9} \right)\left( {x - 10} \right)\left( {x - 11} \right) + 11\left( {x - 8} \right)\left( {x - 9} \right)\left( {x - 10} \right)\\
= 9\left( {x - 8} \right)\left( {x - 10} \right)\left( {x - 11} \right) + 10\left( {x - 8} \right)\left( {x - 9} \right)\left( {x - 11} \right)\\
\to \left( {8x - 72} \right)\left( {{x^2} - 21x + 110} \right) + \left( {11x - 88} \right)\left( {{x^2} - 19x + 90} \right)\\
= \left( {9x - 72} \right)\left( {{x^2} - 21x + 110} \right) + \left( {10x - 80} \right)\left( {{x^2} - 20x + 99} \right)\\
\to - 168{x^2} + 880x - 72{x^2} + 1512x - 7920 - 209{x^2} + 990x - 88{x^2} + 1672x - 7920\\
= - 189{x^2} + 990x - 72{x^2} + 1512x - 7920 - 200{x^2} + 990x - 80{x^2} + 1600x - 7920\\
\to 4{x^2} - 38x = 0\\
\to \left[ \begin{array}{l}
x = 0\\
x = \frac{{19}}{2}
\end{array} \right.\left( {TM} \right)
\end{array}\)
