Question

Find the 23rd term of -12, -15, -18.

Answer 1

do you know what the common ratios is?

Answer 2

The difference is about -3?

Answer 3

So it's an arithmetic series?

Answer 4

ok so the common ratio is -3
the 1st term as you can see, is -12

so now that we know those two fellows we'll use them in \(\Large \bf a_{\color{red}{ n}}=a_1+({\color{red}{ n}}-1){\color{blue}{ d}}
\\ \quad \\
a_1=\textit{first term}\\
{\color{blue}{ d}}=\textit{common ratio}
\\ \quad \\
\Large a_{\color{red}{ 23}}=-12+({\color{red}{ 23}}-1){\color{blue}{ -3}}\)

Answer 5

-12 + 22 - 3 = 7?

Answer 6

well... the 22 * -3

Answer 7

Oh I read that as subtract 3.

Answer 8

-78?

Answer 9

hmm my bad .... \(\large a_{\color{red}{ n}}=a_1+({\color{red}{ n}}-1){\color{blue}{ d}}
\\ \quad \\
a_1=\textit{first term}\\
{\color{blue}{ d}}=\textit{common ratio}
\\ \quad \\
\large a_{\color{red}{ 23}}=-12+({\color{red}{ 23}}-1)({\color{blue}{ -3}})\)

Answer 10

-78? \(\Large \checkmark\)

Answer 11

So for other problems, I just find the difference and plug in the values?

Answer 12

yeap

Answer 13

Thanks :)

Answer 14

yw