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QJEEM22Mab1a7: JEE Main 2022 Mathematics - Class 12 JEEM22Mab1a7 Solution: Let f, g : R R be two real valued functions defined as f ( x )…

Let f, g : R →\to R be two real valued functions defined as f(x)={−|x+3|,x<0ex,x≥0 and g(x)={x2+k1x,x<04x+k2,x≥0, where k1 and k2 are real constants. If (gof) is differentiable at x = 0, then (gof) ( −- 4) + (gof) (4) is equal to :

Multiple Choice Options

  • A 4(e4+1)4({e^4} + 1)
  • B 2(2e4+1)2(2{e^4} + 1)
  • C 4e44{e^4}
  • D 2(2e4−1)2(2{e^4} - 1)

Step-by-Step Verified Solution

∵\because gof is differentiable at x = 0

So R.H.D = L.H.D

ddx(4ex+k2)=ddx((−∣x+3∣)2−k1∣x+3∣){d \over {dx}}(4{e^x} + {k_2}) = {d \over {dx}}\left( {{{( - |x + 3|)}^2} - {k_1}|x + 3|} \right)

⇒4=6−k1⇒k1=2\Rightarrow 4 = 6 - {k_1} \Rightarrow {k_1} = 2

Also f(f(0+))=g(f(0−))f(f({0^ + })) = g(f({0^ - }))

⇒4+k2=9−3k1⇒k2=−1\Rightarrow 4 + {k_2} = 9 - 3{k_1} \Rightarrow {k_2} = - 1

Now g(f(−4))+g(f(4))g(f( - 4)) + g(f(4))

=g(−1)+g(e4)=(1−k1)+(4e4+k2)= g( - 1) + g({e^4}) = (1 - {k_1}) + (4{e^4} + {k_2})

=4e4−2= 4{e^4} - 2

=2(2e4−1)= 2(2{e^4} - 1)

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