Answer
$3$
Work Step by Step
We do what we have to according to the exercise: $$f'(1)=\lim_{x\to 1}\frac{f(x)-f(1)}{x-1}=\lim_{x\to 1}\frac{-4+3x-(-1)}{x-1}=\lim_{x\to 1}\frac{-3+3x}{x-1}=\lim_{x\to 1}\frac{3(x-1)}{x-1}=\lim_{x\to 1}3=3.$$
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