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QJEEM24Maf348: JEE Main 2024 Mathematics - Class 12 JEEM24Maf348 Solution: Suppose for a differentiable function and . If , then is equal…

Suppose for a differentiable function h,h(0)=0,h(1)=1h, h(0)=0, h(1)=1 and h′(0)=h′(1)=2h^{\prime}(0)=h^{\prime}(1)=2 . If g(x)=h(ex)eh(x)g(x)=h\left(\mathrm{e}^x\right) \mathrm{e}^{h(x)} , then g′(0)g^{\prime}(0) is equal to:

Multiple Choice Options

  • A 4
  • B 5
  • C 3
  • D 8

Step-by-Step Verified Solution

To determine g′(0)g^{\prime}(0) , we start by applying the chain rule and product rule to find the derivative of the given function g(x)=h(ex)eh(x)g(x) = h\left(\mathrm{e}^x\right) \mathrm{e}^{h(x)} .

The product rule states that if we have two functions u(x)u(x) and v(x)v(x) , then the derivative of their product is given by:

(u(x)v(x))′=u′(x)v(x)+u(x)v′(x)(u(x)v(x))' = u'(x)v(x) + u(x)v'(x)

Let's denote u(x)=h(ex)u(x) = h(\mathrm{e}^x) and v(x)=eh(x)v(x) = \mathrm{e}^{h(x)} .

First, we need to find u′(x)u'(x) and v′(x)v'(x) . Using the chain rule, we find:

u′(x)=ddxh(ex)=h′(ex)⋅ddx(ex)=h′(ex)⋅exu'(x) = \frac{d}{dx}h(\mathrm{e}^x) = h'(\mathrm{e}^x) \cdot \frac{d}{dx}(\mathrm{e}^x) = h'(\mathrm{e}^x) \cdot \mathrm{e}^x

Now, the derivative of v(x)v(x) is:

v′(x)=ddx(eh(x))=eh(x)⋅h′(x)v'(x) = \frac{d}{dx}(\mathrm{e}^{h(x)}) = \mathrm{e}^{h(x)} \cdot h'(x)

Using the product rule, we get the derivative of g(x)g(x) :

g′(x)=u′(x)v(x)+u(x)v′(x)g'(x) = u'(x) v(x) + u(x) v'(x)

Substituting u(x)u(x) , v(x)v(x) , u′(x)u'(x) , and v′(x)v'(x) into the above expression, we get:

g′(x)=(h′(ex)ex)eh(x)+(h(ex))(eh(x)h′(x))g'(x) = \left( h'(\mathrm{e}^x) \mathrm{e}^x \right) \mathrm{e}^{h(x)} + \left( h(\mathrm{e}^x) \right) \left( \mathrm{e}^{h(x)} h'(x) \right)

Next, we need to evaluate this at x=0x = 0 :

First, we know that:

h(0)=0h(0) = 0

h(1)=1h(1) = 1

h′(0)=2h'(0) = 2

h′(1)=2h'(1) = 2

Substituting x=0x = 0 into the expressions, we get:

u(0)=h(e0)=h(1)=1u(0) = h(\mathrm{e}^0) = h(1) = 1

v(0)=eh(0)=e0=1v(0) = \mathrm{e}^{h(0)} = \mathrm{e}^0 = 1

u′(0)=h′(e0)e0=h′(1)⋅1=2u'(0) = h'(\mathrm{e}^0) \mathrm{e}^0 = h'(1) \cdot 1 = 2

v′(0)=eh(0)h′(0)=e0⋅2=2v'(0) = \mathrm{e}^{h(0)} h'(0) = \mathrm{e}^0 \cdot 2 = 2

Therefore, evaluating g′(0)g'(0) :

g′(0)=(u′(0)v(0))+(u(0)v′(0))g'(0) = \left( u'(0) v(0) \right) + \left( u(0) v'(0) \right)

g′(0)=(2⋅1)+(1⋅2)g'(0) = \left( 2 \cdot 1 \right) + \left( 1 \cdot 2 \right)

g′(0)=2+2=4g'(0) = 2 + 2 = 4

Thus, the value of g′(0)g^{\prime}(0) is 4, which corresponds to Option A.

The correct answer is Option A: 4.

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