### maximum of a two variable polynomial by fixing one of them

I have a Polynomial of two variables f(x,y) . I want to find the maximum of the function for a fixed value of y that depends on y and x changes on a closed interval. basically i want to find ~~Max(f(x,b) ~~$Max f(x,b)$ : ~~b ~~b$ is a constant and ~~0<x<1 ).="" is="" there="" any="" way="" to="" do="" that="" in="" sage="" and="" the="" result="" be="" a="" function="" in="" y.<="" p="">
~~$0 \leq x \leq 1$ ). Is there any way to do that in sage and the result be a function in y.