1)(3х-1)(9х²+3х+1)-9х(3х²-4)=17
27х³-1-27х³-36х=17
-1-36х=17
-36х=18
х=-0,5
_______________________________
(х+4)(х²-4х+16)-х(х-7)(х+7)=15
х³+64-х(х²-49)=15
х³+64-х³-49х=15
64-49х=15
-49х=-64-15
49х=79
______________________________
(х+6)(х²-12х+36)-х(х-9)²=4х (4,5х-13,5)
х³+216-х(х²-18х+81)=18х²-54х
х³+216-х³+18х-81х=18х²-54х
216-81х=-54х
-27х=-216
х=8