i have this function

and f(x,y)=0 on point (0,0)

i dont know the proper english term

i need to prove that f(x,y) is deferentialbe

so by the definition

and i need to find those epsilons which will make the sude to be equal

and both epsilons will go to zeroo when x and y are going to zero

i dont know what to put instead of "f" in each term

because the function is stplitted