logo

Ask Questions, Get Answers

 
X
 Search
Want to ask us a question? Click here
Browse Questions
Ad
0 votes

If $f(x)=log\bigg(\large\frac{1+x}{1-x}\bigg)$, then $f(x)+f(y)$ = ?

$\begin{array}{1 1} f(x+y) \\f(xy) \\f\bigg(\large\frac{x+y}{1+xy}\bigg) \\ f\bigg(\large\frac{x+y}{1-xy}\bigg) \end{array}$

Can you answer this question?
 
 

1 Answer

0 votes
Toolbox:
  • $log(ab)=loga+logb$
Ans- (C)
given: $f(x)=log\bigg(\large\frac{1+x}{1-x}\bigg)$
$f(x)+f(y)=log\bigg(\large\frac{1+x}{1-x}\bigg)+log\bigg(\large\frac{1+y}{1-y}\bigg)$
$=log\bigg(\large\frac{1+x+y+xy}{1-x-y+xy}\bigg)$
Divide num. and deno. by (1+xy)
$=log\bigg(\large\frac{1+\frac{x+y}{1+xy}}{1-\frac{x+y}{1+xy}}\bigg)$
$=f\bigg(\large\frac{x+y}{1+xy}\bigg)$
answered May 8, 2013 by rvidyagovindarajan_1
edited May 17, 2014 by rohanmaheshwari0831_1
 
Ask Question
student study plans
x
JEE MAIN, CBSE, NEET Mobile and Tablet App
The ultimate mobile app to help you crack your examinations
Get the Android App
...