Question

Write a formula for the general term or nth term for the sequence. Then find the indicated term. five halves comma five fourths comma five eighths comma five sixteenths ...; a 8 a Subscript nequals ?

Answer 1

Sequence: 5/2, 5/4, 5/8, 5/16
a8=?

a1=5/2
a2=5/4
a3=5/8
a4=5/16

a2/a1=(5/4)/(5/2)=(5/4)*(2/5)=(5*2)/(4*5)=2/4=1/2
a3/a2=(5/8)/(5/4)=(5/8)*(4/5)=(5*4)/(8*5)=4/8=1/2
a4/a3=(5/16)/(5/8)=(5/16)*(8/5)=(5*8)/(16*5)=8/16=1/2
Ratio: r=a2/a1=a3/a2=a4/a3→r=1/2

an=a1*r^(n-1)
a1=5/2, r=1/2
an=(5/2)*(1/2)^(n-1)
an=(5/2)*[1^(n-1)/2^(n-1)]
an=(5/2)*[1/2^(n-1)]
an=(5*1)/[2*2^(n-1)]
an=5/2^(1+n-1)
an=5/2^n

n=8→a8=5/2^8
a8=5/256

Answers:
The formula for the general term or nth term for the sequence is an=5/2^n
a8=5/256