Second Derivative Ratio
1. **Problem Statement:**
Find the second derivative $f''(x)$, the ratio $\frac{f'(x)}{f(x)}$, and the expression $f''(x) - 2$ for the function $f(x)$ defined by the triangle vertices $(0,0)$, $(3,3)$, and $(6,0)$.
2. **Step 1: Define the function $f(x)$**
The triangle vertices suggest a piecewise linear function:
- From $x=0$ to $x=3$, the line passes through $(0,0)$ and $(3,3)$, so slope $m_1 = \frac{3-0}{3-0} = 1$.
- From $x=3$ to $x=6$, the line passes through $(3,3)$ and $(6,0)$, so slope $m_2 = \frac{0-3}{6-3} = -1$.
Thus,
$$
f(x) = \begin{cases}
x & 0 \leq x \leq 3 \\
- x + 6 & 3 < x \leq 6
\end{cases}
$$
3. **Step 2: Find $f'(x)$**
Since $f(x)$ is piecewise linear,
$$
f'(x) = \begin{cases}
1 & 0 < x < 3 \\
-1 & 3 < x < 6
\end{cases}
$$
Note: $f'(x)$ is not defined at $x=3$ due to the corner.
4. **Step 3: Find $f''(x)$**
The derivative of a constant slope is zero everywhere except at the corner where the slope changes abruptly.
Thus,
$$
f''(x) = 0 \quad \text{for} \quad x \neq 3
$$
At $x=3$, $f''(x)$ is undefined (a Dirac delta in distribution sense), but for typical calculus,
$$
f''(x) = 0 \quad \text{almost everywhere}
$$
5. **Step 4: Compute $\frac{f'(x)}{f(x)}$**
For $0 < x < 3$:
$$
\frac{f'(x)}{f(x)} = \frac{1}{x}
$$
For $3 < x < 6$:
$$
\frac{f'(x)}{f(x)} = \frac{-1}{-x + 6} = \frac{1}{x - 6}
$$
Note: At $x=0$ or $x=3$ or $x=6$, the expression is undefined due to division by zero or derivative discontinuity.
6. **Step 5: Compute $f''(x) - 2$**
Since $f''(x) = 0$ almost everywhere,
$$
f''(x) - 2 = 0 - 2 = -2 \quad \text{for} \quad x \neq 3
$$
**Final answers:**
- $f''(x) = 0$ for $x \neq 3$
- $\frac{f'(x)}{f(x)} = \begin{cases} \frac{1}{x} & 0 < x < 3 \\ \frac{1}{x - 6} & 3 < x < 6 \end{cases}$
- $f''(x) - 2 = -2$ for $x \neq 3$
These results reflect the piecewise linear nature of $f(x)$ and its derivatives.