1.

If \(f(x) = \frac{1+x}{1-x}\) ,  then the value of f [f (x)] is(a) x (b) \(\frac{1}{x}\)c) – x (d) \(-\frac{1}{x}\)

Answer»

Answer : (d) = \(-\frac{1}{x}\) 

Given f(x) = \(\frac{1+x}{1-x}\) 

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

\(\frac{2}{-2x}\) 

\(-\frac{1}{x}\)



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