So, why am I subtracting 1 from both the parabolas ( in y= form ) in the first problem, and in the second problem, what's up with the limits of integration ( I.E. part A it's 0 to 16, part B it isn't doubled, it's 0 to 16 again IIRC ), and why in part B, when I solve for Y=x^3/4, am I integrating from 0 to 8 ((16^2) - (16 - x^3/4 ) )^2 all multiplied by pi?

I'm not even sure why I'm subtracting x^3/4 from 16, and my book ( "Calculus, Early Trascendentals, by Varberg, Purcell, and Rigdon" ) is useless at explaining the concept behind it as it uses exclusively high brained vocabulary to the point I have to try to rewrite what it's saying - literally translate it - at times.