1. The problem asks to find the interval where the function $f(x) = 3|x + 1| - 2$ is increasing.
2. Recall that the absolute value function $|x|$ is defined as:
$$|x| = \begin{cases} x & \text{if } x \geq 0 \\ -x & \text{if } x < 0 \end{cases}$$
3. For $f(x) = 3|x + 1| - 2$, the critical point is where the expression inside the absolute value changes sign, i.e., at $x = -1$.
4. Consider two cases:
- For $x \geq -1$, $|x + 1| = x + 1$, so
$$f(x) = 3(x + 1) - 2 = 3x + 3 - 2 = 3x + 1$$
- For $x < -1$, $|x + 1| = -(x + 1) = -x - 1$, so
$$f(x) = 3(-x - 1) - 2 = -3x - 3 - 2 = -3x - 5$$
5. Now, find the derivative (rate of change) in each interval:
- For $x \geq -1$, $f'(x) = 3$ (positive, so $f$ is increasing here)
- For $x < -1$, $f'(x) = -3$ (negative, so $f$ is decreasing here)
6. Therefore, the function is increasing on the interval $]-1, \infty[$.
7. The correct answer is A) $]-1, \infty[$.
Increasing Interval
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