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If the width is w and the length is l, then 2w+2l=perimeter=34=2*6.5+2l=13+2l. Subtracting 13 from both sides, we get 21=2l and by dividing both sides by 2 we get 10.5
First term (a) = -31
Common Difference (d) = -27 - (-31) = -27 + 31 = 4
nth term = a + (n - 1)d = -31 + (n - 1)4 = -31 + 4n - 4 = 4n - 35
Hence, the formula is 4n - 35.
