Solution
Step 1: Define the polynomial function
Let the second-degree polynomial be:
Step 2: Use the given condition f(1)=f(−1)
A(1)2+B(1)+C=A(−1)2+B(−1)+C
So, the function is:
Step 3: Find the derivative f′(x)
Differentiating with respect to x:
Step 4: Evaluate at a,b,c
Given a,b,c are in Arithmetic Progression (AP), they satisfy:
b−a=c−b=d (common difference)
Now, find the values of the derivatives:
Step 5: Check the progression of f′(a),f′(b),f′(c)
Find the difference between consecutive terms:
f′(b)−f′(a)=2Ab−2Aa=2A(b−a)=2Ad
f′(c)−f′(b)=2Ac−2Ab=2A(c−b)=2Ad
Since the common difference is constant (2Ad), the terms f′(a),f′(b),f′(c) are in AP.
Final Answer:
The correct option is 4.