how do I save equations on a ti-36x pro for future calculations?

Can anyone help me on how to save functions on a ti 36x pro for future calculations?



I am doing a lot of plug and chug calculus and physics problems that would save me time if I knew how to save the functions and real them later, by changing what x is.



Ie. Newtons method to finding roots when the domain is not given. Linearization (relative error) etc.



Thanks. I will give big hug to first poster