The given expression is a geometric progression:

3¹ + 3² + 3³ + ...

+ 3⁸

Here, first term a = 3, common ratio r = 3, and number of terms n = 8.

Sum of GP = a(r^n − 1)/(r − 1)

= 3(3^8 − 1)/(3 − 1)
= 3(6561 − 1)/2
= 3(6560)/2
= 3 × 3280
= 9840.