А)(х-1)(х-3)(х-5)=(х^2-3х-х+3)(х-5)=(х^2-4х+3)(х-5)=х^3-5х^2-4х^2+20х+3х-15=х^3-9х^2+23х-15............................................................,................
б) х(х-1)(х-2)-х^2 (х-3)=х (х^2-2х-х+2)-х^3+3х^2=х^3-2х^2-х^2+2х-х^3+3х^2=2х................................................................................................
в)(у-1)(у^4+у^3+у^2+у+1)=у^5+у^4+у^3+у^2+у-у^4-у^3-у^2-у-1=у^5-1...
г) (n+1)(n^4-n^3+n^2-n+1)=n^5-n^4+n^3-n^2+n+n^4-n^3+n^2-n+1=n^5+1