Question

5.-10. 20.-40.... determine if arithmetic,geometrical or neither​

Answer 1

Geometric progression.

Explanation:

I suppose you mean this equation:

5, -10, 20, -40, ...

For a geometric progression, an n^th term is given by:

`a_(n)` =
`a_(n - 1)` × r

Where a is the first time, n is the term and r is the common ratio.

The common ratio here is -2 .

For instance to check the forth term;

`a_(4)` =
`5_(4 - 1)` × -2 = 20 × -2 = -40

Answer 2

It is a geometrical progression

Explanation:

Geometric progressions have a constant number that they are multiplied by

To find that number you divide the 2nd term by the 1st term and also the 4th term by the 3rd term. ie,

`(-40)/(20) = (-10)/(5) \\`

`-2 = -2`

since they are both equal it is a G.P

Because they have a constant ratio.