Answer:
arithmetic
Explanation:
The points fall on a straight line. They won't do that for a geometric sequence.
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Normally the terms of either sort of sequence are numbered with counting numbers: 1, 2, 3, .... Your x-values are negative, so are obviously not term numbers of a sequence. The differences of x-values are 1, and the differences of y-values are 2.5, so we know the x- and y-values are linearly related. That relationship can be expressed in point-slope form by ...
y = 2.5(x +1) +12.5
which can be simplified to
y = 2.5x +15
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The arithmetic sequence with first term 17.5 and common difference 2.5 would be described by this same equation.