SOLUTION: 124 is the ____ term of the arithmetic sequence -2, 5, 12,...

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Question 969083: 124 is the ____ term of the arithmetic sequence -2, 5, 12,...
Answer by Fombitz(32388) About Me  (Show Source):
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a%5B1%5D=a%5B0%5D%2Bd=-2
a%5B2%5D=a%5B0%5D%2B2d=5
Subtract the first from the second,
a%5B0%5D%2B2d-a%5B0%5D-d=5-%28-2%29
d=7
Then,
a%5B0%5D%2B7=-2
a%5B0%5D=-9
So,
a%5Bn%5D=-9%2B7d=124
7n=133
n=19
124 is the 19th term.