(a一2b十3c)(a十3b一3c)
=a²+3ab-3ac-2ab-6b²+6c+3ac+9bc-9c²
(a一2b十3c)(a十2b一3c)
=a²一(2b一3c)²
=a²-4b²+12bc-9c²
(a一3b十3c)(a十2b一3c)
=a²一(3b一3c)²
=a²-9b²+18bc-9c²
(a一2b十3c)(a十3b一3c)
=a²+3ab-3ac-2ab-6b²+6c+3ac+9bc-9c²
(a一2b十3c)(a十2b一3c)
=a²一(2b一3c)²
=a²-4b²+12bc-9c²
(a一3b十3c)(a十2b一3c)
=a²一(3b一3c)²
=a²-9b²+18bc-9c²