(2х³+1)²-4х³=(4х⁶+4х³+1)-4х³=4х⁶+4х³+1-4х³=4х⁶+1
(7х+8у)²-7х²=49х²+112ху+64у²-7х²=42х²+112ху+64у²
(х-у)(х²+ху+у²)+у³-1=(х³+х²у+ху²-х²у-ху²-у³)++у³-1=х³-у³+у³-1=х³-1
(2х-у)²-(3х+2у)²=(4х²-4ху+у²)-(9х²+12ху+4у²)=4х²-4ху+у²-9х²-12ху-4у²=-5х²-16ху-3у²
