Câu 18:
Tính limx→1−x2+3x−4∣x−1∣\mathop {\lim }\limits_{x \to {1^ - }} \frac{{{x^2} + 3x - 4}}{{\left| {x - 1} \right|}}x→1−lim∣x−1∣x2+3x−4.
