Sign Derivative 990A74
1. The problem asks to find the sign of the function $f$ given its derivative $f'(x) = \frac{x^2 - 4x + 3}{(x-2)^2}$.
2. To determine where $f$ is increasing or decreasing, we analyze the sign of $f'(x)$.
3. The denominator $(x-2)^2$ is always positive except at $x=2$ where it is undefined.
4. Focus on the numerator $x^2 - 4x + 3$; factor it:
$$x^2 - 4x + 3 = (x-1)(x-3)$$
5. The critical points from the numerator are $x=1$ and $x=3$.
6. The derivative $f'(x)$ is undefined at $x=2$ due to the denominator.
7. Test intervals determined by points $1$, $2$, and $3$:
- For $x < 1$, pick $x=0$: numerator $(0-1)(0-3) = (-1)(-3) = 3 > 0$, denominator positive, so $f'(x) > 0$.
- For $1 < x < 2$, pick $x=1.5$: numerator $(1.5-1)(1.5-3) = (0.5)(-1.5) = -0.75 < 0$, denominator positive, so $f'(x) < 0$.
- For $2 < x < 3$, pick $x=2.5$: numerator $(2.5-1)(2.5-3) = (1.5)(-0.5) = -0.75 < 0$, denominator positive, so $f'(x) < 0$.
- For $x > 3$, pick $x=4$: numerator $(4-1)(4-3) = (3)(1) = 3 > 0$, denominator positive, so $f'(x) > 0$.
8. Summary of $f'(x)$ sign:
- Increasing on $(-\infty, 1)$
- Decreasing on $(1, 2)$ and $(2, 3)$
- Increasing on $(3, \infty)$
9. Note that $f'(x)$ is undefined at $x=2$, so $f$ may have a vertical tangent or discontinuity there.
Final answer: $f$ is increasing on $(-\infty, 1)$ and $(3, \infty)$, decreasing on $(1, 2)$ and $(2, 3)$.