CUET · MATHS · PYQ PAPER 2023

The minimum value of \(a x+b y\), where \(x y=c^2\) and \(a, b, c\) are positive, is:

A \(2 b \sqrt{a c}\)
B \(2 a \sqrt{b c}\)
C \(2 c \sqrt{a b}\)
D \(2 \sqrt{a b c}\)

Verified Solution

Answer & Solution

Correct Answer

(C) \(2 c \sqrt{a b}\)

Step-by-step Solution

Detailed explanation

\(ax+by \geq 2\sqrt{(ax)(by)}\) \(ax+by \geq 2\sqrt{ab(c^2)}\) \(ax+by \geq 2c\sqrt{ab}\)

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.

Same subject

If \(P(A)=\frac{2}{5}, P(B)=\frac{3}{10}\) and \(P(A \cap B)=\frac{1}{5}\), then \(P\left(A^{\prime} / B^{\prime}\right) \cdot P\left(B^{\prime} / A^{\prime}\right)\) is equal to :

CUET 2023 Hard

Match List-I with List-II

List-I	List-II
(A) A square matrix P is said to be non-singular if	(I) \(\|P\|=0\)
(B) A square matrix P is said to be singular if	(II) \(P P^T\) is symmetric
(C) If a matrix P is both symmetric and skew-symmetric, then	(III) \(\|P\| \neq 0\)
(D) If P is a square matrix, then	(IV) \(P\) is a null matrix

Choose the correct answer from the options given below :

CUET 2025 Hard

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