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If f(x)=x2−4x+13,x∈Rf(x) = x^2 - 4x + 13, x \in \mathbb{R}, then which of the following are correct?

(A) x=2x = 2 is a stationary point of f(x)f(x).

(B) f(x)f(x) is increasing function on (2,∞)(2, \infty)

(C) f(x)f(x) have maxima at x=2x = 2

(D) f(2)=9f(2) = 9

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 4

Given f(x)=x2−4x+13,x∈Rf(x) = x^2 - 4x + 13, x \in \mathbb{R}

The derivative is:

f′(x)=2x−4f'(x) = 2x - 4


For statement (A): A stationary point occurs when f′(x)=0f'(x) = 0.

2x−4=02x - 4 = 0

2x=42x = 4

x=2x = 2

Statement (A) is correct.


For statement (B): The function is increasing when f′(x)>0f'(x) > 0.

For x>2x > 2:

f′(x)=2x−4f'(x) = 2x - 4

Since x>2x > 2, we have 2x>42x > 4

Therefore 2x−4>02x - 4 > 0

Statement (B) is correct.


For statement (C): The second derivative is:

f′′(x)=2f''(x) = 2

Since f′′(2)=2>0f''(2) = 2 > 0, the function has a minimum at x=2x = 2, not a maximum.

Statement (C) is incorrect.


For statement (D): Substitute x=2x = 2 into the function:

f(2)=(2)2−4(2)+13f(2) = (2)^2 - 4(2) + 13

f(2)=4−8+13f(2) = 4 - 8 + 13

f(2)=9f(2) = 9

Statement (D) is correct.


Statements (A), (B), and (D) are correct.

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