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QJEEM22Ma8e02: JEE Main 2022 Mathematics - Class 11 JEEM22Ma8e02 Solution: The number of real solutions of the equation is ___________.

The number of real solutions of the equation e4x+4e3x−58e2x+4ex+1=0{e^{4x}} + 4{e^{3x}} - 58{e^{2x}} + 4{e^x} + 1 = 0 is ___________.

Step-by-Step Verified Solution

Dividing by e2x

e2x+4ex−58+4e−x+e−2x=0{e^{2x}} + 4{e^x} - 58 + 4{e^{ - x}} + {e^{ - 2x}} = 0

⇒(ex+e−x)2+4(ex+e−x)−60=0\Rightarrow {({e^x} + {e^{ - x}})^2} + 4({e^x} + {e^{ - x}}) - 60 = 0

Let ex+e−x=t∈[2,∞){e^x} + {e^{ - x}} = t \in [2,\infty )

⇒t2+4t−60=0\Rightarrow {t^2} + 4t - 60 = 0

⇒t=6\Rightarrow t = 6 is only possible solution

ex+e−x=6⇒e2x−6ex+1=0{e^x} + {e^{ - x}} = 6 \Rightarrow {e^{2x}} - 6{e^x} + 1 = 0

Let ex=p{e^x} = p ,

p2−6p+1=0{p^2} - 6p + 1 = 0

⇒p=3+52\Rightarrow p = {{3 + \sqrt 5 } \over 2} or 3−52{{3 - \sqrt 5 } \over 2}

So x=ln⁡(3+52)x = \ln \left( {{{3 + \sqrt 5 } \over 2}} \right) or ln⁡(3−52)\ln \left( {{{3 - \sqrt 5 } \over 2}} \right)

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