Algebra 2 help! thanks just 3 questions?
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What is the 20th term of the arithmetic sequence 4, –2, –8, … ?
–110
–116
–122
–128
What is the sum of a 17–term arithmetic sequence where the first term is 9 ...show more
Best Answer
1).
What is the 20th term of the arithmetic sequence 4, –2, –8, … ?
–110
2).
What is the sum of a 17–term arithmetic sequence
where the first term is 9 and the last term is –87?
Difference = 96/17
5< D < 6
9 + 4 + (1) + (6) + ...... +(71)> 527
9 + 3 + (3) + (9) + ...... +(87)) 663
–663
3).
The 17th term of the arithmetic sequence 17, 21, 25, … ?
81
What is the 20th term of the arithmetic sequence 4, –2, –8, … ?
–110
2).
What is the sum of a 17–term arithmetic sequence
where the first term is 9 and the last term is –87?
Difference = 96/17
5< D < 6
9 + 4 + (1) + (6) + ...... +(71)> 527
9 + 3 + (3) + (9) + ...... +(87)) 663
–663
3).
The 17th term of the arithmetic sequence 17, 21, 25, … ?
81
Other Answers (4)
Rated Highest
1. Looks like it follows the equation 106n where n is the number of the term
thus the 20th term is 106(20) or 10120 = 110
2. Let the equation be A+nB
the first term is A+B = 9
the 17th term is A+17B=87
equation 2 less equation 1 is 16B = 96..........B = 6 .......A = 15
so the 17term sequence starts with 156(1)...156(2)......to 156(17)
the sum is 15(17)6(sum 1 to 17)........................sum (117) is 17(17+1)/2 = 153
thus 15(17) 6(153)
= 255  918
= 663
3. looks like the formula there is 13 + 4n
so the 17th term is 13 + 4(17)
= 13 + 68
= 81 
the last one is 85

1) 110
2)718
3) 79Source(s):
prealgebra student [; 
You are using the equation An= A1 + (n1)d
1) A1= 4(first number) n= 20( number of term you want) d= 6 ( you are taking away 6 to get to each new term)
Now just plug in and solve:
An= 4 + (201)(6)
Answer: 110
Now use the equation Sn= n/2(An+A1)
2) n=17 An=87 A1=9
Plug in and solve:
Sn= (17/2)(87 + 9)
Answer: 663
Use An= A1 + (n1)d again
3) n=17 A1=17 d=+4
Plug in and solve:
An= 17 + (171)(4)
Answer: 81Source(s):
Math Teacher
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