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QJEEM24Ma84f0: JEE Main 2024 Mathematics - Class 12 JEEM24Ma84f0 Solution: The values of , for which , lie in the interval

The values of α\alpha , for which ∣1amp;32amp;α+321amp;13amp;α+132α+3amp;3α+1amp;0∣=0\left|\begin{array}{ccc}1 & \frac{3}{2} & \alpha+\frac{3}{2} \\ 1 & \frac{1}{3} & \alpha+\frac{1}{3} \\ 2 \alpha+3 & 3 \alpha+1 & 0\end{array}\right|=0 , lie in the interval

Multiple Choice Options

  • A (−2,1)(-2,1)
  • B (−32,32)\left(-\frac{3}{2}, \frac{3}{2}\right)
  • C (−3,0)(-3,0)
  • D (0,3)(0,3)

Step-by-Step Verified Solution

∣1amp;32amp;α+321amp;13amp;α+132α+3amp;3α+1amp;0∣=0\left|\begin{array}{ccc}1 & \frac{3}{2} & \alpha+\frac{3}{2} \\1 & \frac{1}{3} & \alpha+\frac{1}{3} \\2 \alpha+3 & 3 \alpha+1 & 0\end{array}\right|=0

amp;⇒(2α+3){7α6}−(3α+1){−76}=0amp;⇒(2α+3)⋅7α6+(3α+1)⋅76=0amp;⇒2α2+3α+3α+1=0amp;⇒2α2+6α+1=0amp;⇒α=−3+72,−3−72\begin{aligned}& \Rightarrow(2 \alpha+3)\left\{\frac{7 \alpha}{6}\right\}-(3 \alpha+1)\left\{\frac{-7}{6}\right\}=0 \\& \Rightarrow(2 \alpha+3) \cdot \frac{7 \alpha}{6}+(3 \alpha+1) \cdot \frac{7}{6}=0 \\& \Rightarrow 2 \alpha^2+3 \alpha+3 \alpha+1=0 \\& \Rightarrow 2 \alpha^2+6 \alpha+1=0 \\& \Rightarrow \alpha=\frac{-3+\sqrt{7}}{2}, \frac{-3-\sqrt{7}}{2}\end{aligned}

Hence option (C) is correct.

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