Question

What is the fifteenth term of the sequence

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

1)-163 840

2)-81.920

3)81,920

4)327.680

Answer 1

81920.

Explanation:

1) the ration of the given sequence is -2=-10/5=20/(-10)...

2) the 15th term can be calculated according to the formula:

a₁₅=a₁*(ratio)¹⁴, then

a₁₅=5*(-2)¹⁴=-5*1024*16=81920.