Ответ:

1)(х-3у)²-(3х-у)²=х²+9у²-6ху-(9х²+у²-6ху)=х²+9у²-6ху-9х²-у²+6ху=-8х²+8у²=-8×(-3)²+8×(3½)²=-8×9+8×12¼=-72+98=26

2)(m+5)²-(m-4)(m+4)=

m²+25+10m-(m²-16)=m²+25+10m-m²+16=

10m+41=10×(-3,5)+41=6

3)(a³-2)(a³+2)-(a³+3)²

=(a³)²-2²-((a³)²+9+6a³)=a^6-4-(a^6+9+6a³)=a^6-4

-a^6-9-6a³=-4-9-6a³=-13-6a³=35