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NARAYANA IIT/PMT ACADEMY - Narayanaicc.com

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<strong>NARAYANA</strong> <strong>IIT</strong>/<strong>PMT</strong> <strong>ACADEMY</strong><br />

JEE ADVANCE : 2013<br />

(PAPER – II) CODE: 0<br />

PART – III : MATHEMATICS<br />

SECTION – 1 (Only or more options correct Type)<br />

This section contains 8 multiple choice questions Each question has four choices (A) (B), (C) and (D)<br />

out of the which ONE or MORE are correct<br />

41 Let be a <strong>com</strong>plex cube root of unity with 1 and P p<br />

ij<br />

be a n n matrix with<br />

Ans<br />

Sol<br />

2<br />

Then P 0, when n =<br />

(A) 57 (B) 55 (C) 58 (D) 56<br />

(B,C,D)<br />

1 1 ... ... 1 1 ... ...<br />

2 2 2 2<br />

2 2<br />

1 ... 1 ...<br />

1 ... 1 ...<br />

2 2<br />

... ... ... ... ... ...<br />

2 2<br />

1 ... 1 ...<br />

..... .....<br />

... ...<br />

p<br />

ij<br />

i<br />

j<br />

Clearly P 2 will be O if n is a multiple of 3, then only, the elements of P 2 will be reduced to<br />

2<br />

1 0<br />

2<br />

If P 0 n is not multiple of 3<br />

42 The function y 2 | x | | x 2 | | x 2 | 2 | x | has a local minimum or a local maximum at x =<br />

(A) 2<br />

(B)<br />

Ans (A, B)<br />

Sol y 2 | x | | x 2 | | x 2 | 2 | x |<br />

2<br />

3<br />

Case (i) x 2<br />

y 2x x 2 | x 2 2x |<br />

y 3x 2 | x 2|<br />

y 2x 4 … (1)<br />

Case (ii) 2 x 0<br />

y x 2 | 3x 2|<br />

So for x<br />

2<br />

3<br />

y 2x 4 … (2)<br />

(C) 2 (D) 2 3<br />

<strong>NARAYANA</strong> GROUP OF EDUCATIONAL INSTITUTIONS - INDIA<br />

25

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