grandes-ecoles 2015 QIII.B.2

grandes-ecoles · France · centrale-maths2__mp Reduction Formulae Prove Regularity or Structural Properties of an Integral-Defined Function
For $( x , y )$ in $\left( \mathbb { R } ^ { + * } \right) ^ { 2 }$, we define $\beta ( x , y ) = \int _ { 0 } ^ { 1 } t ^ { x - 1 } ( 1 - t ) ^ { y - 1 } \mathrm {~d} t$.
Let $x > 0$ be fixed. What is the monotonicity on $\mathbb { R } ^ { + * }$ of the function $y \mapsto \beta ( x , y )$?
For $( x , y )$ in $\left( \mathbb { R } ^ { + * } \right) ^ { 2 }$, we define $\beta ( x , y ) = \int _ { 0 } ^ { 1 } t ^ { x - 1 } ( 1 - t ) ^ { y - 1 } \mathrm {~d} t$.

Let $x > 0$ be fixed. What is the monotonicity on $\mathbb { R } ^ { + * }$ of the function $y \mapsto \beta ( x , y )$?