Marriage vows joke

Some variables were getting married.

I, dependent variable Y, take you independent variable X, to be my husband to have and to hold from this day forward, for better or for worse, for richer, for poorer, in differentiation and in integration, to multiply and to exponentiate; from this day forward until death do us part.

The priest said “Now I pronounce you dependent and independent variable, husband and wife in all matters of differentiation and integration.”

Someone from the audience says “until someone applies the variable separable methods on you, do you remain husband and wife”.