Question

Consider the following geometric sequence -5, 10, -20, 40,..... if the recursive formula for the sequence above expressed in the form a(n)=b*a(n-1), determine the value of b.

b=
2
-2
5
-5

Answer 1

Use a(n) = 10 as a starting point and create an equation:

a(n) = b * a(n-1)

10 = b * -5
b = -2

Answer 2

value of b = -2

Explanation:

Consider the following geometric sequence -5, 10, -20, 40,..... if the recursive formula for the sequence above expressed in the form a(n)=b*a(n-1)

first we write the recursive formula for the given sequence

To get the recursive formula we find common ratio

Common ration = second term divide by first term

10/-5= -2

-20/ 10= -2

a(n)=common ratio *a(n-1)

a(n)=(-2)*a(n-1)

So b = -2