Question

Fie functia f:(-1,1)→R, f(x)=㏑$\frac{1+x}{1-x}$ . Calculati f(-x)+f(x), x∈(-1,1)

Answer 1

$\it f(-x) +f(x) = ln\dfrac{1-x}{1+x}+ln\dfrac{1+x}{1-x}=ln\left(\dfrac{1-x}{1+x}\cdot\dfrac{1+x}{1-x}\right) =ln1=0$