Question 1092279
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The first term is 23 - 13 = 10.


The common difference is -3.


The equation for the last term, x, is  


x + (x+3) = -25,


which implies  2x = -28, x = -14.


So, the progression is 13, 10, 7, 4, 1, -2, -5, -8, -11, -14.


10 terms with the sum of -5.
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