Ответ:

5(а+9)-(2а+3)(а-1) = 5а+45-(2а²-2а+3а-3) = 5а+45-2а²+2а-3а+3 = -2а²+4а+48

8(а-4)+(3а-1)(а+2) = 8а-32+(3а²+6а-а-2) = 8а-32+3а²+6а-а-2 = 3а²+13а-34

(1-а)(7+а)-(а+6)(а-6) = (7+а-7а-а²)-(а²-6а+6а-36) = (7-6а-а²)-(а²-36) = 7-6а-а²-а²+36 = -2а²-6а+43