SOLUTION: which term in the sequence -3, -6, -9, -12...is -30?

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Question 1185748: which term in the sequence -3, -6, -9, -12...is -30?



Found 2 solutions by ikleyn, math_helper:
Answer by ikleyn(52788) About Me  (Show Source):
You can put this solution on YOUR website!
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The sequence is  a%5Bn%5D = -3n,  n = 1, 2, 3, . . . 


The number  " -30 "  is the 10-th term of the sequence.

Solved.



Answer by math_helper(2461) About Me  (Show Source):
You can put this solution on YOUR website!


First term a%5B1%5D = -3

2nd term +a%5B2%5D+ = -6



Common difference is -3



Nth term is +a%5BN%5D+ = -3 - 3*(N - 1)



So we set a%5BN%5D+=+-30 and solve for N:

-30 = -3 + -3*(N-1)

 -27 = -3*(N-1)

 N-1 = 9

  N = 10  (the 10th term is -30)