algebra
posted by Marissa
1)Find the 20th term of the arithmetic sequence in which a1=3 and d=7
a.143
b.136
c.140
d.133
an=a1+(n1)d
a20=3+(201)7
a20=3+(19)7
a20=3+133
answer=b
2)Write an equation for the nth term of the arithmetic sequence 3,3,9,15...
a.an=n+6
b.an=6n+9
c.an=6n9
d.an=n3
an=a1+(n1)d
an=3+(n1)6
an=36n+6
answer=b
3)Find the two arithmetic means between 4 and 22
a.10,16
b.8,16
c.8,12
d.13,13
an=a1+(n1)d
a6=4+(61)d
22=4+6d
answer=a
4)Simplify:Find Snfor the arithmetic series in which a1=3,d=1/2,and an=15
a.225
b.9
c.45
d.210
Sn=n/2(a1+an)
Sn=15/2(3+15)
answer=b
5)I don't know how to type this but its like this in my book.
Find; 8 is on top of the sigma notation and k=3 is at the bottom(403k) is on the right side
a.45
b.282
c.90
d.141
403(3)=409=31
403(4)=4012=28
403(5)=4015=25
403(6)=4018=22
403(7)=4021=19
403(8)=4024=16
answer=d

bobpursley
2. Isn't a1=3, and d=+6 ?
3I have no idea what the question is asking.
5.
Sum= sigma(k=3,8) of (403k)
(403*3)+(403*4) + ... as you wrote the terms.
It will break down to
40*(82)  3(3+4+5+6+7+8)=2403*33=24099= 141 as upi determined.
=
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