$$f(x_{1}, y_{1}, y_{2}, ..., y_{n}) = \dfrac{x_{1}y_{m}}{\log_{2} \left(1+\dfrac{a}{b+(\sum_{i=1}^n \ \ y_{i})-y_{m}}\right)}$$ on$\{(x_{1},y_{i})\in[0,1]\}$,and$\{a,b,m\}$ is constant,$\{m\in\{1..n\}\}$.
Is there any way to prove that it's convex or not?
Any help would be appreciated.