Question

Find the eight term of the geometric sequence for which a_1 = 5 and r = ­-2.

Answer 1

T8 = -640

Explanation:

`a =5\\r = -2\\Tn = ar^(n-1) \\T8 =5(-2)^8^-^1\\T8 = 5(-2)^7\\T8 = 5* -128\\T8 = -640`

Answer 2

For a geometric sequence

U(n) = ar^n-1

where

a = first term

r = common ratio

n= number of terms

From the above statement

a = 5

r = -2

n = 8

U(8) = 5(-2)^8-1

= 5(-2)^7

= - 640

Hope this helps