Question

Would someone mind helping me with this quick precalc question? I have no idea how to solve this!

Find an equation for the nth term of the arithmetic sequence.

a19 = -58, a21 = -164

Here are my choices:

an = 896 - 53(n - 2)
an = 896 - 53(n - 1)
an = 896 + 53(n + 1)
an = 896 - 53(n + 1)

Answer 1

I've never worked with a problem like this before...

Answer 2

for option a) we test like:
\(a_\color{red}{n}= 896-53 (\color{red}{n}-2)\)
\(a_\color{red}{19} = 896 -53(\color{red}{19}-2)\)
You calculate \( a_{19}=??\)

Answer 3

I got -5 for a19

Answer 4

Oh! So a must not be the answer because a19 is supposed to equal -58

Answer 5

Yes, it is -5 for \(a_{19}\) of that formula while our \(a_{19} = -58\)

Answer 6

ok, test option b
show me your understanding.

Answer 7

an = 896 - 53(n - 1)
a19 = 896 - 53(19-1)
a19=-58
B is my answer!

Answer 8

have to test \(a_{21}\) also, to make sure that you are not lucky when getting it.

Answer 9

Yes, i tested a21 and got 896 - 53(21-1) and it was -164

Answer 10

Bingo!! congrats

Answer 11

Thank you so much for helping me understand this! Really appreciate it!

Answer 12

np