Question

The graph of the even function \( y = f'(x) \) consists of 4 line segments, as shown above. Which of the following statements about \( f \) is false?
A) \( \lim_{x\rightarrow 0}(f(x)-f(0))=0 \)
B) \( \lim_{x\rightarrow 0}\frac{f(x)-f(-x)}{x}=0 \)
C) \( \lim_{x\rightarrow 0} \frac{f(x)-f(-x)}{2x}=0 \)
D) \( \lim_{x\rightarrow 2}\frac{f(x)-f(2)}{x-2}=1 \)
E) \( \lim_{x\rightarrow 3}\frac{f(x)-f(3)}{x-3} \) does not exist
▶️ Answer/Explanation
Solution
Correct Answer: B
Since \( f’ \) is even, \( f \) is not necessarily even. Statement B resembles the derivative of an odd function, and is not guaranteed to be true. Therefore, statement B is false.
Question
(A) The function is continuous at x = 3
(B) The limit as x approaches 3 exists
(C) The function has a removable discontinuity at x = 3
(D) The function has a jump discontinuity at x = 3
(E) The function is differentiable at x = 3
▶️ Answer/Explanation
Solution
Correct Answer: D
1. Evaluate the function at x = 3:
– Left approach (x→3⁻): \( f(3^-) = 2(3) – 2 = 4 \)
– Right approach (x→3⁺): \( f(3^+) = 2(3) – 4 = 2 \)
– Actual value: \( f(3) = 2(3) – 4 = 2 \)
2. Analyze continuity and differentiability:
– The left and right limits are different (4 ≠ 2)
– The function value equals the right limit (f(3) = 2)
– This creates a jump discontinuity at x = 3
Key observations:
• (A) False – Not continuous (left ≠ right limit)
• (B) False – Limit doesn’t exist (left ≠ right)
• (C) False – Not removable (finite jump)
• (D) True – Jump discontinuity present
• (E) False – Not differentiable (not continuous)
Question
The derivative of a function f is given by \( f'(x) = 0.2x + e^{0.15x} \). Which of the following procedures can be used to determine the value of x at which the line tangent to the graph of f has slope 2?
A) Evaluate \( 0.2x + e^{0.15x} \) at x=2
B) Evaluate \( \frac{d}{dx}(0.2x + e^{0.15x}) \) at x=2
C) Solve \( 0.2x + e^{0.15x} = 2 \) for x
D) Solve \( \frac{d}{dx}(0.2x + e^{0.15x}) = 2 \) for x
▶️ Answer/Explanation
Solution
Correct Answer: C
Key Concept:
The derivative \( f'(x) \) represents the slope of the tangent line to the graph of \( f \) at any point \( x \).
Solution Steps:
1. We need to find where the tangent slope equals 2
2. Set the derivative equal to 2: \( 0.2x + e^{0.15x} = 2 \)
3. Solve this equation for \( x \) (option C)
Note: The equation \( 0.2x + e^{0.15x} = 2 \) would typically be solved numerically or graphically, as it cannot be solved algebraically.
Question
The derivative of the function f is given by \( f'(x) = -2x + 4 \) for all x, and \( f(-1) = 5 \). Which of the following is an equation for the line tangent to the graph of f at \( x = -1 \)?
A) \( y = -2x + 3 \)
B) \( y = -2x + 4 \)
C) \( y = 6x + 5 \)
D) \( y = 6x + 11 \)
▶️ Answer/Explanation
Solution
Correct Answer: D
Step 1: Find the slope at \( x = -1 \)
\( f'(-1) = -2(-1) + 4 = 2 + 4 = 6 \)
Step 2: Use the given point \( (-1, 5) \)
We know the tangent line passes through this point with slope 6.
Step 3: Write the equation in point-slope form
\( y – 5 = 6(x – (-1)) \)
\( y = 6(x + 1) + 5 \)
Step 4: Simplify to slope-intercept form
\( y = 6x + 6 + 5 \)
\( y = 6x + 11 \)