The given values
.
The sum of a geometric series is
.
Where
is first term and r is common ratio.
(Substitute
)
(Subtract denominator:
)
Apply multiplication property of equality: a = b then 
(Multiply each side by
)
(Cancel common terms)
(Evaluate powers:
)
(Subtract:
)
(Multiply:
)
Apply multiplication property of equality: a = b then 
(Multiply each side by
)
(Cancel common terms)
(Multiply:
)
The value of
.