Ta có: \(\dfrac{x-3}{x-2}-\dfrac{x-2}{x-4}=1\dfrac{5}{21}\)
\(\Leftrightarrow\dfrac{21\left(x-3\right)\left(x-4\right)}{21\left(x-2\right)\left(x-4\right)}-\dfrac{21\left(x-2\right)^2}{21\left(x-2\right)\left(x-4\right)}=\dfrac{26\left(x-2\right)\left(x-4\right)}{21\left(x-2\right)\left(x-4\right)}\)
\(\Leftrightarrow26\left(x^2-6x+8\right)=21\left(x^2-7x+12\right)-21\left(x^2-4x+4\right)\)
\(\Leftrightarrow26x^2-156x+208=21x^2-147x+252-21x^2+84x-84\)
\(\Leftrightarrow26x^2-156x+208+63x-168=0\)
\(\Leftrightarrow26x^2-93x+40=0\)
\(\text{Δ}=\left(-93\right)^2-4\cdot26\cdot40\)
\(=8649-4160\)
\(=4489\)
Vì Δ>0 nên phương trình có hai nghiệm phân biệt là:
\(\left\{{}\begin{matrix}x_1=\dfrac{93-67}{52}=\dfrac{1}{2}\left(nhận\right)\\x_2=\dfrac{93+67}{52}=\dfrac{40}{13}\left(nhận\right)\end{matrix}\right.\)
