Question

Write an expression that gives the requested sum.

Answer 1

Answer:

The expression to give the requested sum after simplifying, $S_{20}$ = ${3(3^{20}-1) }$

Step-by-step explanation:

To find the sum of first 20 terms,

a = 6, r = 3

By formula, $S_{n} = \frac{a(r^{n}-1) }{r-1}$

substitute the values in the above formula, the equation becomes,

$S_{20} = \frac{6(3^{20}-1) }{3-1}$

$S_{20} = \frac{6(3^{20}-1) }{2}$

$S_{20}$ = ${3(3^{20}-1) }$