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JEE Advanced 2015Paper 1
Exam
JEE Advanced
Year
2015
Paper
Paper 1
Subject
Mathematics
Chapter
Determinants

JEE Advanced 2015 · Paper 1 · Mathematics · Determinants

Which of the following values of α satisfy the equation | cases (1...

Which of the following values of α\alpha satisfy the equation \left|{(1+α)2(1+2α)2(1+3α)2(2+α)2(2+2α)2(2+3α)2(3+α)2(3+2α)2(3+3α)2\begin{cases}{\left(1 + \alpha\right)}^{2} & {\left(1 + 2\alpha\right)}^{2} & {\left(1 + 3\alpha\right)}^{2} \\ {\left(2 + \alpha\right)}^{2} & {\left(2 + 2\alpha\right)}^{2} & {\left(2 + 3\alpha\right)}^{2} \\ {\left(3 + \alpha\right)}^{2} & {\left(3 + 2\alpha\right)}^{2} & {\left(3 + 3\alpha\right)}^{2}\end{cases}\right| = - 648\alpha$ ?

Options

  1. A−4- 4
  2. B99
  3. C−9- 9
  4. D44

Correct answer

B. 99

Step-by-step solution

\left|{(1+α)2(1+2α)2(1+3α)2(2+α)2(2+2α)2(2+3α)2(3+α)2(3+2α)2(3+3α)2\begin{cases}{\left(1 + \alpha\right)}^{2} & {\left(1 + 2\alpha\right)}^{2} & {\left(1 + 3\alpha\right)}^{2} \\ {\left(2 + \alpha\right)}^{2} & {\left(2 + 2\alpha\right)}^{2} & {\left(2 + 3\alpha\right)}^{2} \\ {\left(3 + \alpha\right)}^{2} & {\left(3 + 2\alpha\right)}^{2} & {\left(3 + 3\alpha\right)}^{2}\end{cases}\right|<br><br><br ><br >{R}_{2} \to {R}_{2} - {R}_{1}(Takecommon)<br>(Take common) <br >{R}_{3} \to {R}_{3} - {R}_{1}<br><br><br ><br >2\left|{(1+α)2(1+2α)2(1+3α)23+2α(3+4α)(3+6α)(4+2α)(4+4α)(4+6α)\begin{cases}{\left(1 + \alpha\right)}^{2} & {\left(1 + 2\alpha\right)}^{2} & {\left(1 + 3\alpha\right)}^{2} \\ 3 + 2\alpha & \left(3 + 4\alpha\right) & \left(3 + 6\alpha\right) \\ \left(4 + 2\alpha\right) & \left(4 + 4\alpha\right) & \left(4 + 6\alpha\right)\end{cases}\right|<br><br><br ><br >{R}_{3} \to {R}_{3} - {R}_{2}<br><br><br ><br >2\left|{(1+α)2(1+2α)2(1+3α)23+2α3+4α3+6α111\begin{cases}{\left(1 + \alpha\right)}^{2} & {\left(1 + 2\alpha\right)}^{2} & {\left(1 + 3\alpha\right)}^{2} \\ 3 + 2\alpha & 3 + 4\alpha & 3 + 6\alpha \\ 1 & 1 & 1\end{cases}\right|<br><br><br ><br >{C}_{2} \to {C}_{2} - {C}_{1}(Takecommon)<br>(Take common) <br >{C}_{3} \to {C}_{3} - {C}_{1}<br><br><br ><br >∴ 2\alpha2 . \alpha \left|\begin{cases}{\left(1 + \alpha\right)}^{2} & \left(2 + 3\alpha\right) & \left(2 + 4\alpha\right) \\ 3 + 2\alpha & 2 & 2 \\ 1 & 0 & 0\end{cases}\right|

4α2∣−2α∣4{\alpha}^{2}\left|- 2\alpha\right| = - 8{\alpha}^{3} = - 648\alpha<br><br >\alpha = 0, {\alpha}^{2} = 81, \alpha = \pm 9
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