Answers

2015-07-06T18:43:02+08:00
X should be 3
3+2=5
3(3)-2=7
7(3)-12=9
5,7,9 form an arithmetic sequence because it has a common difference which is 2
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2015-07-06T18:46:20+08:00

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We should have a common difference for these to be terms of an arithmetic sequence so:

7x - 12 - 3x + 2 = 3x - 2 - x - 2
4x - 10 = 2x - 4
2x = 6
x = 3

When we plug this value the terms would be 5, 7, and 9 which have a common difference of 2.
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