Correct Answer - Option 3 : x = 2
Following steps to finding maxima and minima using derivatives:
Step-1: Find the derivative of the function.
Step-2: Set the derivative equal to 0 and solve. This gives the values of the maximum and minimum points.
Step-3: Now we have to find the second derivative.
Case-1: If f"(x) is less than 0 then the given function is said to be maxima
Case-2: If f"(x) Is greater than 0 then the function is said to be minima
f(x) = x2 - 4x
Differentiating with respect to x, we get
⇒ f'(x) = 2x - 4
For minimum value, f'(x) = 0
⇒ 2x - 4 = 0
∴ x = 2
Again differentiating with respect to x, we get
⇒ f"(x) = 2 > 0
Hence f(x) attains minimum value at x = 2