1)6(х+1)²+2(х-2)(х²+х+2)-2(х+1)³ = 6(х²+2х+1)+2(х³-1)-х³+3х²+3х+1 = 6х²+12х+6+2х³-2-х³+3х²+3х-1 = 8х²+15х+7

2)5х(х-3)²-5(х-1)³+15(х+2)(х-2) = 5х(х²-6х+9)-5(х³-3х²+3х-1) = 5х³-30х²+45х-5х³+15х²-15х+5 = -15х²+30х+5

3)(х+2)³-х(3х+1)²+(2х+1)(4х²-2х+1) = х³+6х²+24+8-3х²-х+8х³+1 = 9х³+3х²+33