Answer
$D$
Work Step by Step
Firstly, we will have to multiply numerator by reciprocal of the denominator, such as:
$\dfrac{x-1}{x+3} \div \dfrac{1}{x-4}$
$=(x-4) \times \dfrac{x-1}{x+3}$
$=\dfrac{(x-4)(x-1)}{x+3}$
$=\dfrac{x^2-x-4x+4}{x+3}$
$=\dfrac{x^2-5x+4}{x+3}$
Hence, the correct answer is $D$.
