Custom Maxima functions at startup?

I do a lot of dB calculations and parallel resistors, impedances, etc.
I wrote these functions and operator (idb = inverse dB):

db(x):=float(20*log(x)/log(10));
idb(x):=float(10^(x/20));
INFIX("||")$ "||"(x,y):=x*y/(x+y);

1. I have to cut and paste these every time I start Maxima to use
them. Is there a way to make it load them automatically at startup without me typing anything?

2. Would they conflict with any built-in functions or operators if I
did?

I am using Maxima 5.9.0 in Windows XP.

Thanks,
Jon




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