Find an equation for the nth term of the arithmetic sequence.
a19 = -92, a20 = 6
an = -1856 + 98(n - 1)
an = -1856 - 98(n - 1)
an = -1856 - 98(n + 1)
an = -1856 + 98(n + 1)
@dan815 @jim_thompson5910 @mathstudent55 @compassionate @zzr0ck3r

- anonymous

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- jim_thompson5910

First isolate d
\[\Large a_{19} + d = a_{20}\]
\[\Large -92 + d = 6\]
\[\Large d= ???\]

- anonymous

-86 @jim_thompson5910

- anonymous

then what do we do? @jim_thompson5910

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## More answers

- jim_thompson5910

you add 92 to both sides

- jim_thompson5910

6+92 = ??

- anonymous

98 @jim_thompson5910

- jim_thompson5910

so d = 98

- jim_thompson5910

which is why the answer is
|dw:1436316159029:dw|

- jim_thompson5910

|dw:1436316211464:dw|

- jim_thompson5910

first term is \[\Large a_1 = -1856\]
|dw:1436316259108:dw|

- jim_thompson5910

common difference is d = 98
we add 98 to each term to get the next term
|dw:1436316282925:dw|

- anonymous

so a is the final answer? @jim_thompson5910

- jim_thompson5910

yeah

- jim_thompson5910

|dw:1436316316037:dw|

- anonymous

can u help me with another one? @jim_thompson5910

- jim_thompson5910

sure

- anonymous

Find an equation for the nth term of the arithmetic sequence.
-17, -13, -9, -5, ...
an = -17 + 4(n + 2)
an = -17 x 4(n - 1)
an = -17 + 4(n - 1)
an = -17 + 4(n + 1)

- jim_thompson5910

what's the first term?

- anonymous

i dont know @jim_thompson5910

- jim_thompson5910

just look at the first number given in the sequence

- anonymous

-17 @jim_thompson5910

- jim_thompson5910

yeah

- jim_thompson5910

what must we add to -17 to get to the next term -13 ?

- anonymous

4 @jim_thompson5910

- jim_thompson5910

so d = 4

- jim_thompson5910

First term
\[\Large a_1 = -17\]
Common difference
\[\Large d = 4\]

- jim_thompson5910

|dw:1436316606279:dw|

- anonymous

so the answer would be c?
@jim_thompson5910

- jim_thompson5910

|dw:1436316636005:dw|

- jim_thompson5910

|dw:1436316659391:dw|

- jim_thompson5910

yes, c

- anonymous

Find an equation for the nth term of a geometric sequence where the second and fifth terms are -2 and 16, respectively.
an = 1 â€¢ (-2)n - 1
an = 1 â€¢ 2n
an = 1 â€¢ (-2)n + 1
an = 1 â€¢ 2n - 1
@jim_thompson5910 one more?

- jim_thompson5910

show me what you have so far

- anonymous

i dont have anything? i dont know how to do it?

- anonymous

@jim_thompson5910

- jim_thompson5910

second term = -2
third term = -2*r = -2r
fourth term = (-2r)*r = -2r^2
fifth term = (-2r^2)*r = -2r^3
-------------------------------------------------------
solve for r
-2r^3 = 16

- anonymous

how do i do thta? @jim_thompson5910

- jim_thompson5910

you need to isolate r
try to get r all by itself

- jim_thompson5910

think to yourself
-2 times _________ = 16
what goes in the blank?

- anonymous

r

- jim_thompson5910

-2 times _________ = 16
think of a number that goes in the blank

- anonymous

i got 1.25

- anonymous

@jim_thompson5910

- jim_thompson5910

no

- anonymous

so what is it?

- jim_thompson5910

this article may help
http://www.purplemath.com/modules/solvelin.htm

- jim_thompson5910

it shows how to solve equations

- anonymous

i dont know? im stupid lol @jim_thompson5910

- jim_thompson5910

read that article a few times. It should help
you aren't stupid

- anonymous

can u show me step by step im more of a visual person @jim_thompson5910

- jim_thompson5910

for example
2 times x = 10 means x = 5
since 2 times 5 = 10

- jim_thompson5910

2q = 28 means q = 14
because 2 times 14 = 28

- jim_thompson5910

you can divide both sides by 2 to isolate the variable

- anonymous

so then its r^3=-8 @jim_thompson5910

- jim_thompson5910

very good

- jim_thompson5910

to undo the cube exponent, we take the cube root of both sides
|dw:1436317751492:dw|

- jim_thompson5910

|dw:1436317761724:dw|

- anonymous

i got this 1Â±iâˆš3

- jim_thompson5910

|dw:1436317773660:dw|

- jim_thompson5910

only focus on the real solutions

- jim_thompson5910

|dw:1436317819217:dw|

- anonymous

so the answer is a?

- jim_thompson5910

|dw:1436317839091:dw|

- jim_thompson5910

yeah it's the only one that fits

- jim_thompson5910

so a1 has to be 1

- anonymous

one last one? @jim_thompson5910

- anonymous

Write the sum using summation notation, assuming the suggested pattern continues.
-1 + 2 + 5 + 8 + ... + 44
summation of negative three times n from n equals zero to fifteen
summation of the quantity negative one plus three n from n equals zero to fifteen
summation of negative three times n from n equals zero to infinity
summation of the quantity negative one plus three n from n equals zero to infinity

- anonymous

@jim_thompson5910 @UsukiDoll

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