4x2 - 25y

It seems like you have an expression, \(4x^2 - 25y\). If you're looking to simplify or factor it, can you please clarify whether you want to do something specific with it?

For instance, if you're inclined to factor it, the expression could be factored if it were set equal to zero, or if you have a particular context (like finding its roots or analyzing it), please provide more details!