a1 = 6 an+1=-2an+3

help pleaseee!!

Question

a1 = 6 an+1=-2an+3

help pleaseee!!

anonymous · Answer

I need the first 5 terms! i'm confused on how to solve this

pfenn1 · Answer

Do you mean this is a series of equations where$$a _{1}=6$$$$a _{n+1}=-2a _{n}+3$$?

anonymous · Answer

yeah

pfenn1 · Answer

so $$a _{1}=6$$$$a _{2}=-2a _{1}+3=-2(6)+3=-9$$$$a _{3}=?$$

anonymous · Answer

Oh... wow okay thanks can you help me with another one?

pfenn1 · Answer

You should be able to do the next ones by yourself.  Just use the equation....$$a _{3}=-2a _{2}+3=$$What would be the answer to this?

anonymous · Answer

21.. 

but i mean like okay if you're being asked for the general term, would you answer with the general term formula?

pfenn1 · Answer

Yes, I think so.  I'm not sure if I was asked for the "general term" I would know what they were asking about.

anonymous · Answer

Okay. for this one: 3, 12, 21, 30, 39 

I was asked to write a formula for the general term and then use the formula to find the 20th term

my answers were an = 3+(n-1)9 and a20 = 174.. But my teacher marked it wrong and I don't understand why. Do you mind doing it to see if you get something different?

pfenn1 · Answer

I think I came up with the same answer you got.  [$$a _{1}=3$$Each next term is 9 more than the term before.  So the general formula would be$$a _{n}=a _{n-1}+9$$ Then $$a _{20}=a _{19}+9=(a _{18}+9)+9=((a _{17}+9)+9)+9=...$$$$=a _{1}+9+9+9+9+9+9+9+9+9+9+9+9+9+9+9+9+9+9+9$$$$=a _{1}+19(9)$$which is$$a _{n+1}=a _{1}+(n-1)9$$Which is exactly what you got?  So I don't know why your teacher says you are wrong.  You might have to re-ask this question and see if anyone else can help.