$\bf \qquad \qquad \textit{sum of a finite geometric sequence} \\\\ S_n=\displaystyle\sum \limits_{i=1}^{n}\ a_1\cdot r^{i-1}\implies S_n=a_1\left( \cfrac{1-r^n}{1-r} \right)\quad \begin{cases} n=n^{th}\ term\\ a_1=\textit{first term's value}\\ r=\textit{common ratio} \end{cases} \\\\[-0.35em] ~\dotfill$

$\bf S_{20}=\displaystyle\sum \limits_{n=1}^{\stackrel{\stackrel{n}{\downarrow }}{20}}~\stackrel{\stackrel{a_1}{\downarrow }}{3}(\stackrel{\stackrel{r}{\downarrow }}{1.5})^{n-1}\implies S_{20}=3\left(\cfrac{1-1.5^{20}}{1-1.5} \right)\implies S_{20}=3\left(\cfrac{1-\stackrel{\approx}{3325.3}}{-0.5} \right) \\\\\\ S_{20}=3\left(\cfrac{-3324.3}{-0.5} \right)\implies S_{20}=3(6648.6)\implies S_{20}=19945.8$

8 0

3 years ago

Read 2 more answers

The sensitive period for language is from 7 months in utero up to 5.5 to 6 years of age. There are several aspects of language f

OleMash [197]

Answer:

The sensitive period for language is from 7 months in utero up to 5.5 to 6 years of age. There are several aspects of language from spoken language, to written language and reading. ... The sensitive period for learning to speak is from is from 7 months to 2.5-3 years of age.

Step-by-step explanation:

7 0

2 years ago

(x+40)° what is x? plssss help meee thank you !!

SVEN [57.7K]

Answer:

I got 103˚ because I put (x+40)˚ into the calculator

5 0

3 years ago