How do you find the sum of the terms of arithmetic -5, -3, -1,1......55?

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Answer 1 · 2016-06-12T00:25:22

We must first determine the number of terms. This can be done by using the formula #t_n = a + (n - 1)d# and solving for #n#.

#55 = -5 + (n - 1)2#

#55 = -5 + 2n - 2#

#55 = -7 + 2n#

#62 = 2n#

#31 = n#

Now, we can use the formula #s_n = n/2(2a + (n - 1)d)#

#s_31 = 31/2(2(-5) + (31 - 1)2)#

#s_31 = 31/2(50)#

#s_31 = 31 xx 25#

#s_31 = 775#

The sum of the terms is #775#.

Hopefully this helps!