` \frac{4}{x - 1} - \frac{5}{x - 2} = 3 `
` <=> \frac{4}{x - 1} - \frac{5}{x - 2} - 3 = 0 `
` <=> \frac{4(x - 2) - 5(x - 1) - 3(x - 1)(x - 2)}{(x - 1)(x - 2)} = 0 `
` <=> \frac{4x - 8 - 5x + 5 - 3x^2 + 6x + 3x - 6}{(x - 1)(x - 2)} = 0 `
` <=> \frac{8x - 9 - 3x^2}{(x - 1)(x - 2)} = 0 `
` <=> 8x - 9 - 3x^2 = 0 `
` <=> 3x^3 - 8x+ 9 = 0 `
` <=> x = \frac{-(-8)^2 ± \sqrt{(-8)^2 - 4.3.9}}{2.3} `
` <=> x = \frac{8±\sqrt{-44}}{6} `
` => ` Vô nghiệm
