What is the Difference between Arithmetic and Geometric Sequence

For each sequence, state if it is arithmetic, geometric, or neither:

1) $-5, \ 15, \ -45, \ 135, \ -405, \ ...$

$\color{red}{r \ = \ \frac{15}{-5} \ = \ -3 \ = \ \frac{-45}{15} \ ⇒ \ geometric}$

2) $7, \ 12, \ 17, \ 22, \ 27, \ ...$

$\color{red}{d \ = \ 12 \ - \ 7 \ = \ 5 \ = \ 17 \ - \ 12 \ ⇒ \ arithmetic}$

3) $56, \ 49, \ 42, \ 35, \ 28, \ ...$

$\color{red}{d \ = \ 49 \ - \ 56 \ = \ -7 \ = \ 42 \ - \ 49 \ ⇒ \ arithmetic}$

4) $78, \ 90, \ 102, \ 114, \ 126, \ ...$

$\color{red}{d \ = \ 90 \ - \ 78 \ = \ 12 \ = \ 102 \ - \ 90 \ ⇒ \ arithmetic}$

5) $48, \ 24, \ 12, \ 6, \ 3, \ ...$

$\color{red}{r \ = \ \frac{24}{48} \ = \ \frac{1}{2} \ = \ \frac{12}{24} \ ⇒ \ geometric}$

6) $192, \ 48, \ 12, \ 3, \ \frac{3}{4} \ , \ ...$

$\color{red}{r \ = \ \frac{48}{192} \ = \ \frac{1}{4} \ = \ \frac{12}{48} \ ⇒ \ geometric}$

7) $-162, \ 54, \ -18, \ 6, \ -2, \ ...$

$\color{red}{r \ = \ \frac{54}{-162} \ = \ -\frac{1}{3} \ = \ \frac{-18}{54} \ ⇒ \ geometric}$

8) $59, \ 46, \ 33, \ 20, \ 7, \ ...$

$\color{red}{d \ = \ 46 \ - \ 59 \ = \ -13 \ = \ 33 \ - \ 46 \ ⇒ \ arithmetic}$

9) $23, \ 39, \ 55, \ 71, \ 87, \ ...$

$\color{red}{d \ = \ 39 \ - \ 23 \ = \ 16 \ = \ 55 \ - \ 39 \ ⇒ \ arithmetic}$

10) $\frac{1}{18} \ , \ \frac{1}{9} \ , \ \frac{2}{9} \ , \ \frac{4}{9} \ , \ \frac{8}{9} \ , \ ...$

$\color{red}{r \ = \ \frac{\frac{1}{9}}{\frac{1}{18}} \ = \ 2 \ = \ \frac{\frac{2}{9}}{\frac{1}{9}} \ ⇒ \ geometric}$