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#1 Re: Help Me ! » Sequences and Series help again! » 2016-05-06 14:19:33

bobbym wrote:

Hi;

3) 162 is the b(5), b(8) is 4374

4) The question has a mistake:

4. v1 = 0.75 and vn = (-2)vk-1 for n>1

You probably mean v(k) = -2 v(k-1)...

That was how the question was written but yeah I think that was what it means.

#2 Help Me ! » Sequences and Series help again! » 2016-05-06 14:02:34

90sginger
Replies: 4

Hi, this is my last algebra lesson and I need to finish this class before May 12th, please help me! I did the questions that I could the best I could. Here is what I really need help with it! I appreciate it!

For questions 3-5, find the first 4 terms and the 8th term of the recursively-defined sequence.

3.  b1 = 2 and bk+1 = 3bk, for k>0
My answer was:
b(1) = 2
b(2) = 3*b1 = 3*2 = 6
b(3) = 3*b2 = 3*6 = 3^2*2 = 9*2 = 18
b(4) = 3*b3 = 3*3^2*2 = 3^3*2 = 54
b(8) = 3^4*2 = 81*2 = 162

My teacher said 8th term not corect, but the others are!

4. v1 = 0.75 and vn = (-2)vk-1 for n>1
My answer was:
v(1) = 3/4
v(2) = -2(3/4)
v(3) = (-2)^2(3/4) = 3
v(4) = (-2)^3(3/4) = -6
v(8) = (-2)^6(3/4) = 48

She said: 2nd and 8th term incorrect

5. c1 = 2, c2 = -1, and ck+2 = ck + ck+1 for k>0
My answer was:
c(1) = 2
c(2) = -1
c(3) = 2+-1 = 1
c(4) = -1 + 1 = 0
c(8) = c(6) + c(5) = [c(4)+c(5)] + c(5) = [0+1+1] = 2

8. The third and sixth terms of a geometric sequence are -75 and -9375 respectively.  Find the first term, the common ratio, and an explicit rule for the nth term.
She said: #8 is tells you the 3rd term is -75 and the 6th term is -9375.  You need to figure out what the 1st term is...and how to get from 1 to the next!

12. Find the sum of the geometric sequence
http://www.sc.whitmoreschool.org/sec/st … age107.gif

For problems 13 and 14, find the sum of the first n terms of the sequence.  The sequences are either arithmetic or geometric.

13.  -1, 11, -121, ...; n = 9

14. 14, 8, 2,...; n=9

#3 Re: Help Me ! » Lesson 20 Sequences and Series » 2016-04-28 06:29:28

bobbym wrote:

You have read the page I sent you to?

Hi, sorry for the late reply, I was sick. Yes, I read the page and tried the best I can but I couldn't understand or was very confused on what to do.

#4 Re: Help Me ! » Lesson 20 Sequences and Series » 2016-04-21 12:19:36

bobbym wrote:

Okay, it is a bit tricky at first so go here.

http://www.mathsisfun.com/algebra/sigma-notation.html

Try to get something out of that and then if you still can not tackle the problems I will do them.

Hi,
I cannot tackle the problems. They still confuse me.

#5 Re: Help Me ! » Lesson 20 Sequences and Series » 2016-04-21 07:28:47

bobbym wrote:

Hi;

No, they are different. Do you know how to use summation notation?

No I do not know how to use summation notation.

#6 Re: Help Me ! » Lesson 20 Sequences and Series » 2016-04-21 04:55:17

bobbym wrote:

Do not forget to reduce v6.

What help do you need with them?

Just how to do them or if they're the same like number 1 and 2

For problems 9 and 10, write each sum using summation notation.
9.2 + 5 + 8 + 11 + ... + 29
10. 6 - 12 + 24 - 48 + ...
11. Find the sum of the arithmetic sequence 2, 4, 6, 8, ..., 70.
12. Find the sum of the geometric sequence
http://www.sc.whitmoreschool.org/sec/students/classes/scalgebra_2/lesson35_files/clip_image107.gif
For problems 13 and 14, find the sum of the first n terms of the sequence.  The sequences are either arithmetic or geometric.
13.  -1, 11, -121, ...; n = 9
14. 14, 8, 2,...; n=9
15. Determine whether the infinite series  is equal to a real number.  If so, find the sum.
http://www.sc.whitmoreschool.org/sec/students/classes/scalgebra_2/lesson35_files/clip_image121.gif

#7 Re: Help Me ! » Lesson 20 Sequences and Series » 2016-04-20 17:11:22

bobbym wrote:

Hi;

Do I stop there or keep going?

You just need v5 and v6 and you are done with the first two questions.

Ah I apologize. I did that and I got:

v5 = 4/5 + 2
v5 = 4/7
v6 = 4/6 + 2
v6 = 4/8

I just need help with the other questions I posted and I'll be good!

#8 Re: Help Me ! » Lesson 20 Sequences and Series » 2016-04-20 16:42:29

Monox D. I-Fly wrote:
90sginger wrote:

d100 = 9,500

Should I put this after the d4?

Nope, he was just testing you. If you can do d1, d2, d3, d4, and d100, surely you can do d5 and d6 by yourself.

Ah okay, I did that and I got:

d5 = (5)^2 - 5(5) 
d5 = 25 - 25 = 0

d6 = (6)^2 - 5(6) 
d6 = 36 - 30 = 6

Do I stop there or keep going?

#9 Re: Help Me ! » Lesson 20 Sequences and Series » 2016-04-20 15:40:04

bobbym wrote:

Yep!

Now what is d100?

d100 = (100)^2 - 5(100)
d100 = 10000 - 500
d100 = 9,500

Should I put this after the d4?

#10 Re: Help Me ! » Lesson 20 Sequences and Series » 2016-04-20 15:15:22

bobbym wrote:

Hmmm. Are you sure 100 * 100 =1000?

100 * 100 = 10,000

#11 Re: Help Me ! » Lesson 20 Sequences and Series » 2016-04-20 13:54:00

bobbym wrote:

That is correct.

What is

for 2)?

d100 = (100)^2 - 5(100)
d100 = 1000 - 500
d100 = 500

#12 Re: Help Me ! » Lesson 20 Sequences and Series » 2016-04-20 11:44:24

bobbym wrote:

Can you reduce that?

v100 = 4/100 + 2 = 4/102 = 2/51

#13 Re: Help Me ! » Lesson 20 Sequences and Series » 2016-04-20 10:21:16

bobbym wrote:

That is correct.

Can you get

v100 = 4/100 + 2 = 4/102

#14 Re: Help Me ! » Lesson 20 Sequences and Series » 2016-04-20 09:51:05

bobbym wrote:

Both v3 and v4 are incorrect, please try again.

v3 = 4/3 + 2 = 4/5
v4 = 4/4 + 2 = 4/6

#15 Re: Help Me ! » Lesson 20 Sequences and Series » 2016-04-20 09:20:25

bobbym wrote:

That is correct and do it for 3).

v3 = 4/3 + 3 = 4/6
v4 = 4/4 + 4 = 4/8

I added v4 just in case.

#16 Re: Help Me ! » Lesson 20 Sequences and Series » 2016-04-20 08:55:52

bobbym wrote:

Start with 1 and plug it into the formula wherever there is an n.

We start with n = 1

What is

V2 = 4/2+2 = 4/4

Should I do the same with V3?

#17 Re: Help Me ! » Lesson 20 Sequences and Series » 2016-04-20 08:29:29

bobbym wrote:

That is correct!

Can you do 1) now or need help.

I need help, if you can!

#18 Re: Help Me ! » Lesson 20 Sequences and Series » 2016-04-20 07:59:38

bobbym wrote:

Hi;

my math is not the greatest

Out of all the billions of people who ever tried to do math only Isaac Newton ever found it easy.

I fixed up your post a bit so everyone can see the problem easily.

Let's try 2)

These are easy, you just start with the counting numbers 1,2,3,4,... and substitute them for n.

Can you do 

for me?

d4 = (4)^2 - 5(4)
d4 = 16 - 20
d4 = -4

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