write an equation to express the geometric sequence 10, 20, 40, 80...

PLEASE ANSWER!!!

Guest Mar 9, 2017

edited by
Guest
Mar 9, 2017

edited by Guest Mar 9, 2017

edited by Guest Mar 9, 2017

edited by Guest Mar 9, 2017

edited by Guest Mar 9, 2017

#2**0 **

Sum =F x (1 - R^N) / (1 - R), where F=First term, R=Common ratio, N=Number of terms.

nth. term =F x R^(N - 1), where F, R and N are the same as above.

Guest Mar 9, 2017

#3**+5 **

**write an equation to express the geometric sequence 10, 20, 40, 80...**

\(\begin{array}{|rcll|} \hline r = \frac{20}{10} = \frac{40}{20} = \frac{80}{40} &=& 2 \\ a&=&10 \\ \hline \end{array}\)

\(\begin{array}{|rcll|} \hline a_n &=& a\cdot r^{n-1} \\\\ a_n &=& 10\cdot 2^{n-1} \\ \hline \end{array}\)

check:

\(\begin{array}{|rcll|} \hline a_1 &=& 10\cdot 2^0 = 10 \\ a_2 &=& 10\cdot 2^1 = 20 \\ a_3 &=& 10\cdot 2^2 = 40 \\ a_4 &=& 10\cdot 2^3 = 80 \\ a_5 &=& 10\cdot 2^4 = 160 \\ \cdots \\ \hline \end{array}\)

heureka
Mar 9, 2017