Answer:
5040
Step-by-step explanation:
-1 × -2 × -3 × -4 × -5 × -6 × -7 × -8 = 40320
40320 ÷ 8 = 5040
(not 100% sure this is right)
Answer: 43.5
a11 = 1
a12 = -1
a21 = -1.5
a13 = 2