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Provide solution for RD Sharma maths class 12 chapter Increasing and Decreasing Functions exercise 16.2 question 18

Answers (1)

Answer:

f(x)=(x-1)e^{x}+1 \text { is an increasing function for all x }> 0.

Given:

f(x)=(x-1)e^{x}+1

To prove:

\text { We have to show that } f(x)=(x-1)e^{x}+1 \text {is an increasing function for all x}>0.

Hint:

f’(x) > 0 is condition for increasing function of f(x).

Solution:

Given

f(x)=(x-1)e^{x}+1

On differentiating both sides w.r.t x we get

\begin{aligned} &\Rightarrow f^{\prime}(x)=\frac{d}{d x}\left[(x-1) e^{x}+1\right] \\ &\Rightarrow f^{\prime}(x)=e^{x}+(x-1) e^{x} \\ &\Rightarrow f^{\prime}(x)=e^{x}(1+x-1) \\ &\Rightarrow f^{\prime}(x)=x e^{x} \\ &\text { As given } x>0 \\ &\Rightarrow e^{x}>0 \\ &\Rightarrow x e^{x}>0 \\ &\Rightarrow f^{\prime}(x)>0 \end{aligned}

Hence condition of f(x) to be increasing is satisfied.

Thus f(x) is increasing on interval x>0

Posted by

Gurleen Kaur

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