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  • Find the derivative of the following functions from first principle. x + 1 x -1

4.(iv)     Find the derivative of the following functions from first principle. \frac{x +1}{x-1}

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best_answer

Given:

f(x)=\frac{x +1}{x-1}

Now, As we know, The derivative of any function at x is 

f'(x)=\lim_{h\rightarrow 0}\frac{f(x+h)-f(x)}{h}

f'(x)=\lim_{h\rightarrow 0}\frac{\frac{x+h+1}{x+h-1}-\frac{x+1}{x-1}}{h}

f'(x)=\lim_{h\rightarrow 0}\frac{\frac{(x+h+1)(x-1)-(x+1)(x+h-1)}{(x-1)(x+h-1)}}{h}

f'(x)=\lim_{h\rightarrow 0}\frac{x^2-x+hx-h+x-1-x^2-xh+x-x-h+1}{(x-1)(x+h-1)h}

f'(x)=\lim_{h\rightarrow 0}\frac{-2h}{(x-1)(x+h-1)h}

f'(x)=\lim_{h\rightarrow 0}\frac{-2}{(x-1)(x+h-1)}

f'(x)=\frac{-2}{(x-1)(x+0-1)}

f'(x)=\frac{-2}{(x-1)^2}  (Answer)

Posted by

Pankaj Sanodiya

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