Question

If the sixth term of a sequence is 128 and the common ratio is 2, then what is the first term?

Answer 1

Geometric progresión:
we can calculate any term, using this rule:
 
an=a₁*r^(n-1)
a₁=the first term
r=the common ratio


a₆=128
r=2

an=a₁ * r^(n-1)
128=a₁ * 2⁶⁻¹
128=a₁ * 2⁵
128=a₁ * 32
a₁=128/32=4

Solution: a₁=4