Question 924361
it has to be a computer glitch.
there's no mathematical reason for it to be there.


the only reason i can think for it to be there would be that (a+b)^4 ends in b^4 when you are dealing with the binomial expansion theorem.


in fact, your original equation is the binomial expansion of (a+b)^3.


that leads me to believe that this is something like an aberrated application of (a+b)^4 where the computer doesn't know to remove 0b^4.


consider:


(a+b) * a = a^2 + ab


now consider:


(a+b) * (a + 0b)


you could get 0b * b = 0b^2 at the end.


in the middle it handles it ok but in the end it sticks out because the algorithm didn't know how to finish the job completely.


(a+b) * (a + 0b) is equal to a*a + a*0b + b*a + 0b*b


this can be simplified to:


a^2 + 0*a*b + a*b + 0*b*b


simplify this further and you get:


a^2 + a*b + 0*b^2


the computer was able to handle 0*a*b + a*b which resulted in a*b.


the computer didn't think it had to do anything else with 0*b*b so it left it as 0*b^2.


bottom line is it doesn't really belong there.


i'm not sure what you were supposed to do with that problem, but i would guess if you got the answer wrong because of that situation, then you have an argument to change that decision.


it's not technically wrong because 0*b^4 is equal to 0, but it doesn't really belong there.