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!