pls help with this expansion of the binomial.
[(6-a)x+ay]^12 ?
Just use the coefficients of Pascal's Triangle, and plug and chug:
((6-a)x)^12 + 12((6-a)x)^11(ay) + ...
See it in all its glory at
http://www.wolframalpha.com/input/?i=[%286-a%29x%2Bay]^12
This is one of those problems that are really pointless. Asking for the 12th power is a cruel joke. It doesn't teach anything more than asking for the 3rd power, which is at least doable.