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QJEEM24Ma1a99: JEE Main 2024 Mathematics - Class 11 JEEM24Ma1a99 Solution: The sum of the solutions of the equation is

The sum of the solutions x∈Rx \in \mathbb{R} of the equation 3cos⁡2x+cos⁡32xcos⁡6x−sin⁡6x=x3−x2+6\frac{3 \cos 2 x+\cos ^3 2 x}{\cos ^6 x-\sin ^6 x}=x^3-x^2+6 is

Multiple Choice Options

  • A 3
  • B 1
  • C 0
  • D −- 1

Step-by-Step Verified Solution

amp;3cos⁡2x+cos⁡32xcos⁡6x−sin⁡6x=x3−x2+6amp;⇒cos⁡2x(3+cos⁡22x)cos⁡2x(1−sin⁡2xcos⁡2x)=x3−x2+6amp;⇒4(3+cos⁡22x)(4−sin⁡22x)=x3−x2+6amp;⇒4(3+cos⁡22x)(3+cos⁡22x)=x3−x2+6amp;x3−x2+2=0⇒(x+1)(x2−2x+2)=0\begin{aligned}& \frac{3 \cos 2 x+\cos ^3 2 x}{\cos ^6 x-\sin ^6 x}=x^3-x^2+6 \\& \Rightarrow \frac{\cos 2 x\left(3+\cos ^2 2 x\right)}{\cos 2 x\left(1-\sin ^2 x \cos ^2 x\right)}=x^3-x^2+6 \\& \Rightarrow \frac{4\left(3+\cos ^2 2 x\right)}{\left(4-\sin ^2 2 x\right)}=x^3-x^2+6 \\& \Rightarrow \frac{4\left(3+\cos ^2 2 x\right)}{\left(3+\cos ^2 2 x\right)}=x^3-x^2+6 \\& x^3-x^2+2=0 \Rightarrow(x+1)\left(x^2-2 x+2\right)=0\end{aligned}

so, sum of real solutions =−1=-1

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