GATE BT 2022 • Q32
NAT • 1 Mark
Section 1: Engineering Mathematics
Calculus
Subtopic: Fundamentals of Calculus
Question Statement:
The maximum value of the function
2
3
( )
3
2
f x
x
x
for
0
x
is ___________.
Official Answer Key:
1 to 1
Step-by-Step Solution & Explanation
### **Step-by-Step Solution & Mathematical Derivation (GATE BT 2022 Q.32)**
**1. Governing Concept & Definition**:
- **Topic**: Differential Calculus & Maxima/Minima
- For a differentiable function $f(x)$, critical points satisfy $f'(x) = 0$, and local maximum occurs when $f''(x) < 0$.
**2. Detailed Step-by-Step Calculation**:
- **Function**:
$f(x) = 3x^2 - 2x^3 \quad \text{for } x > 0$
- **First Derivative**:
$f'(x) = 6x - 6x^2 = 6x(1 - x)$
- **Critical Points for $x > 0$**:
$6x(1 - x) = 0 \implies x = 1$
- **Second Derivative Test**:
$f''(x) = 6 - 12x \implies f''(1) = 6 - 12 = -6 < 0 \quad (\text{Local Maximum})$
- **Maximum Value**:
$f(1) = 3(1)^2 - 2(1)^3 = 3 - 2 = 1$
**3. Final Answer**:
- **Calculated Value**: **1**
- **Official GATE Accepted Range**: **1 to 1**
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