Inflection Point Ratio
1. The problem states that the function \( f(X) = aX^3 - 2X^2 + 4 \) has an inflection point at \( x = \frac{1}{3} \). We need to find the value of \( \frac{f(1)}{f'(1)} \).
2. Start by finding the first derivative \( f'(X) \) and the second derivative \( f''(X) \):
\[ f'(X) = 3aX^2 - 4X \]
\[ f''(X) = 6aX - 4 \]
3. Since \( x = \frac{1}{3} \) is an inflection point, the second derivative equals zero at this point:
\[ f''\left(\frac{1}{3}\right) = 6a \times \frac{1}{3} - 4 = 0 \]
Simplify:
\[ 2a - 4 = 0 \]
\[ 2a = 4 \]
\[ a = 2 \]
4. Substitute \( a = 2 \) back into the original function and first derivative:
\[ f(X) = 2X^3 - 2X^2 + 4 \]
\[ f'(X) = 3 \times 2 X^2 - 4X = 6X^2 - 4X \]
5. Calculate \( f(1) \) and \( f'(1) \):
\[ f(1) = 2(1)^3 - 2(1)^2 + 4 = 2 - 2 + 4 = 4 \]
\[ f'(1) = 6(1)^2 - 4(1) = 6 - 4 = 2 \]
6. Find \( \frac{f(1)}{f'(1)} \):
\[ \frac{f(1)}{f'(1)} = \frac{4}{2} = 2 \]
Answer: 2, which corresponds to option (d).