1) (a -4b)²-8ab-17b=a²-8ab+16b²-8ab-17b=a²-16ab+16b²-17b
2) -9c²+(3c+d)²-d²= -9c² + 9c² +6cd+d²-d²=6cd
3) (5a-6)²-(5a-6)(5a+6)=(5a-6)×(5a-6-(5a+6))=(5a-6)×(5a-6-5a-6)=(5a-6)×(-12)= -12(5a-6)
4) (7b-t)×(t+7b)+(7b+t)²=(7b-t)×(t+7b)+(t+7b)²=(t+7b)×(7b-t+t+7b)=(t+7b)×14b=14b×(t+7b)
5) (9-8b)×(2b+3)+(4b-1)²=18b+27-16b²-24b+16b²-8b+1=-14b+28
6) (11c+3)²-2c×(5,5+33)= 121c²+66c+9-11c²-66c=110c²+9