$\"\"$

The sum of a geometric series is $\"\"$ .

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

The geometric series is 7 + 21 + 63 + ....... to 10 terms.

$\"\"$ .

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

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

$\"\"$ (Evaluate power: $\"\"$ )

$\"\"$ (Subtract numerator: $\"\"$ )

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

The sum of the geometric series is 206,668.