$\"\"$

Apply alternative formula for sum of a geometric series $\"\"$ .

Where $\"\"$ is first term and r is common ratio.

$\"\"$ (Substitute $\"\"$ )

$\"\"$ (Subtract denominator: $\"\"$ )

$\"\"$ (Multiply numerator: $\"\"$ )

Subtract numerator: $\"\"$ .

$\"\"$

$\"\"$ (Divide: $\"\"$ ) $\"\"$

The value of $\"\"$ .