Question

Find an equation for the nth term of a geometric sequence where the second and fifth terms are -21 and 567, respectively.

Answer 1

use\[\Large a_n = a_1 r^{n-1}\]
a2 = -21 so: \[\Large -21 = a_1 r^{2-1} \]so\[\large -21 = a_1 r\]
a5 = 567 so: \[\Large 567 = a_1 r^{5-1} \]so\[\large 567 = a_1 r^4\]

Answer 2

Now solve these two for a1 and r
\[\large -21 = a_1 r\]\[\large 567 = a_1 r^4\]
use substitution, solve the first equation for a1, then plug that into the second equation.

Answer 3

7?

Answer 4

7 for what? I don't know, haven't worked it out.

Answer 5

an = 7 • 3n - 1

Answer 6

That won't work, it doesn't give a second term of -21

Answer 7

7 • (-3)n -

Answer 8

^that works, r=-3

Answer 9

Find the sum of the arithmetic sequence.

17, 19, 21, 23, ..., 35

Answer 10

i gots 79

Answer 11

Has to be bigger than 79 from those numbers.

Just fill in the missing spots and add them all together

17+19+21+...+35 = ?

Answer 12

oh 260

Answer 13

Yep