The sequence is not arithmetic
The recursive formula would be:

This is because the first term, a₁, is 10. A recursive rule is dependent upon the term before it (a(n-1)) and the common ratio. The common ratio, or the number that each term is multiplied by, is -8.
Answer:
Step-by-step explanation:
pythagoras theorem
a^2+b^2=c^2
8^2+x^2=10^2
64+x^2=100
x^2=100-64
x=
x=6 km
Step-by-step explanation:
(3x2 - 2x - 4) (2x2 + x - 3)
6x4 + 3x3 - 9x2 - 4x3 - 2x2 + 6x - 8x2 - 4x + 12
Solving like terms
6x4 - x3 - 19x2 + 2x + 12