CUET · MATHS · PYQ PAPER 2023

The function \(f(x)=2 x^3-3 x^2-12 x+4\) has:
(A) two points of local maxima.
(B) two points of local minima.
(C) one local maxima and one local minima.
(D) no local maxima or local minima.

A C only
B A only
C B only
D D only

Verified Solution

Answer & Solution

Correct Answer

(A) C only

Step-by-step Solution

Detailed explanation

\(f'(x) = 6x^2 - 6x - 12\) \(6x^2 - 6x - 12 = 0 \Rightarrow x^2 - x - 2 = 0 \Rightarrow (x-2)(x+1) = 0 \Rightarrow x = 2, x = -1\) \(f''(x) = 12x - 6\) \(f''(2) = 12(2) - 6 = 18 > 0\) (Local minimum) \(f''(-1) = 12(-1) - 6 = -18 One local maxima and one local minima.

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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The function \(f(x)=2 x^3-3 x^2-12 x+4\) has:(A) two points of local maxima.(B) two points of local minima.(C) one local maxima and one local minima.(D) no local maxima or local minima.

Step-by-step Solution

The function \(f(x)=2 x^3-3 x^2-12 x+4\) has:
(A) two points of local maxima.
(B) two points of local minima.
(C) one local maxima and one local minima.
(D) no local maxima or local minima.