the first term a(sub)0 of a geometric sequence is 64 and the common ratio is -(5/2)

Question

determine a(sub)1

 

Write an explicit formula for this sequence

 

determine a(sub)6

Answer 1

a(0)=64 with a common ratio of (-5/2)

a(1)=64(-5/2)

a(1)=32(-5)

a(1)=-160

formula:  a(n)=a(r)^(n-1)

              a(n)=(-160)(-5/2)^(n-1)

a(6)=(-160)(-5/2)^(6-1)

a(6)=(-160)(-5/2)^5

a(6)=(-160)(-97.65625)

a(6)=15,625

Answer 2

a₁ = 65

r = -2.5

a_n = 65(-2.5)^n-1

a₆ = ?