Math help I don’t get it

Question

Is -5 , 10 , -20 a geometric or arithmetic , what’s the next 3 terms

Answer 1

-5, 10, -20, 40, -80, 160, ...

it's a geometric sequence with common ratio =-2 = r

a1 = -5

an= a1r^(n-1) = -5(-2)^n-1

a6 =-5(-2)^(6-5) = -5(-2)^^5 = -5(-32) = 160

each term in the sequence = -2 times the preceding term

-5 x -2 = 10

10 x -2 = -20

-20 x -2 = 40

40 x -2 = -80

-80 x -2 = 160