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JEE Advanced 2015Paper 1
Exam
JEE Advanced
Year
2015
Paper
Paper 1
Subject
Mathematics
Chapter
Sequences and Series

JEE Advanced 2015 · Paper 1 · Mathematics · Sequences and Series

Column I Column II ( A ) In ℝ ^ 2 , if the magnitude of the...

Column I Column II
(A)( A ) In R2{\mathbb{R}}^{2} , if the magnitude of the projection vector of the vector \alpha\overset{^}{i} + \beta\overset{^}{j} on \sqrt{3}\overset{^}{i} + \overset{^}{j} is 3\sqrt{3} and if α=2+3β,\alpha = 2 + \sqrt{3}\beta, then possible value (s)of∣α∣of | \alpha | is (are) \left(P\right)</td><td>1</td></tr><tr><td></td> <td>1</td> </tr> <tr> <td>( B )</td><td>Letaandbberealnumberssuchthatthefunction</td> <td>Let a and b be real numbers such that the functionf\left(x\right) = \left\{{−3ax2−2,x<1bx+a2,x≥1\begin{cases}- 3a{x}^{2} - 2, & x < 1 \\ bx + {a}^{2}, & x \ge 1\end{cases}\right) is differentiable for all x∈R.x \in \mathbb{R} . Then possible value (s) of a is (are) \left(Q\right)</td><td>2</td></tr><tr><td></td> <td>2</td> </tr> <tr> <td>( C )</td><td>Let</td> <td>Let\omega \ne 1beacomplexcuberootsofunity.Ifbe a complex cube roots of unity. If{\left(3 - 3\omega + 2{\omega}^{2}\right)}^{4n + 3} + {\left(2 + 3\omega - 3{\omega}^{2}\right)}^{4n + 3} + {\left(- 3 + 2\omega + 3{\omega}^{2}\right)}^{4n + 3} = 0thenpossiblevalue(s)ofnis(are)</td><td>(R)then possible value (s) of n is (are)</td> <td>\left(R\right) 3
(D)( D ) Let the harmonic mean of two positive real numbers a and b 4. If q is a positive real number such that a, 5, q, b is an arithmetic progression, then the value (s) of |q – a| is (are) (S)\left(S\right) 4
(T) 5

Options

  1. Aa-t;b-t;c-q;d-s;
  2. Ba-s,t;b-r,s,t;c-q,r,s;d-t;
  3. Ca-p,q;b-p,q;c-p,q,s,t;d-q,t;
  4. Da-r,s;b-s,t;c-s,t;d-q,r,s,t;

Correct answer

C. a-p,q;b-p,q;c-p,q,s,t;d-q,t;

Step-by-step solution

\left(A\right)As∣3α+β2∣=3⇒∣3α+β∣=23As \left|\dfrac{\sqrt{3}\alpha + \beta}{2}\right| = \sqrt{3} ⇒ \left|\sqrt{3}\alpha + \beta\right| = 2\sqrt{3} ...(i)
And, also α=2+3β\alpha = 2 + \sqrt{3}\beta ...(ii)
Solving (i) & (ii), we get
⇒23+4β=±23⇒ 2\sqrt{3} + 4\beta = \pm 2\sqrt{3}
⇒β=0,−3⇒ \beta = 0, - \sqrt{3}
So, α=2\alpha = 2 and −1- 1
i.e, \left|\alpha\right| = 2, 1<br/><br />( B )HereHere- 3a - 2 = b + {a}^{2}...(i)<br/>And...(i)<br />And- 6a = b...(ii)<br/>Solving(i)and(ii),<br/>...(ii)<br />Solving (i) and (ii),<br />- 3a - 2 = - 6a + {a}^{2}<br/><br />⇒ {a}^{2} - 3a + 2 = 0<br/><br />⇒ a = 1, 2<br/>(C)<br />\left(C\right) Here, (3−3ω+2ω2)4n+3{1+ω4n+3+(ω2)4n+3}{\left(3 - 3\omega + 2{\omega}^{2}\right)}^{4n + 3}\left\{1 + {\omega}^{4n + 3} + {\left({\omega}^{2}\right)}^{4n + 3}\right\}<br/><br />⇒ {\left(3 - 3\omega + 2{\omega}^{2}\right)}^{4n + 3}\left\{1 + {\omega}^{4n} + {\omega}^{8n}\right\} = 0<br/>So,<br />So,n = 1, 2, 4, 5<br/>(D)<br />\left(D\right)q - a = 2d<br/>Let<br />Letq - q = \alpha, d = \dfrac{\alpha}{2}<br/><br />a = 5 - \dfrac{\alpha}{2}, b = a + \dfrac{3\alpha}{2} = 5 + \alpha<br/>Now,<br />Now,\dfrac{ab}{a + b} = 2<br/><br />⇒ \dfrac{\left(5 - \dfrac{\alpha}{2}\right)\left(5 + \alpha\right)}{5 - \dfrac{\alpha}{2} + 5 + \alpha} = 2<br/><br />⇒ \alpha = 5, - 2<br/>∣α∣=5,2<br />\left|\alpha\right| = 5, 2
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