Question

Find the first, fourth, and eighth term of the sequence:A(n)=-2•5n-1

Answer 1

An=a1(r)^(n-1)
a1=first term
r=common ratio
n=which term

so
an=-2(5)^(n-1)
first term is -2
4th term is subsitue 4 for n
a4=-2(5)^(4-1)
a4=-2(5)^3
a4=-2(125)
a4=-250
4th term is -250


8th term
a8=-2(5)^(8-1)
a8=-2(5)^7
a8=-2(78125)
a8=-156250
8th term is -156250

Answer 2

A(1) = -2 x 5(1) - 1 = -11

A(4) = -2 x 5(4) -1 = -41

A(8) = -2 x 5(8) -1 = -81