Question

Find the first term of the following geometric sequence ----,42,126,378,1,134

Answer 1

Since it is a geometric sequence each term will be a specific multiple of the term preceding it, called the common ratio...

126/42=378/126=1134/378=3

The sequence is a(n)=a(3)^(n-1) and we know the second term is 42 so:

42=a(3)^(2-1)

42=3a

a=14

So the first term is 14.