Explicación paso a paso:
[tex] \frac{1}{x - 4} - \frac{1}{x - 3} [/tex]
[tex] = \frac{(x - 3) - (x - 4)}{(x - 4)(x - 3)} [/tex]
[tex] = \frac{x - x + 4 - 3}{ {x}^{2} - 3x - 4x + 12} [/tex]
[tex] = \frac{1}{ {x}^{2} - 7x + 12} [/tex]
