3 years ago

Find S15 for the series -1 + -3 + -5 + -7 +...

1 answer:

Ber [7]3 years ago

8 0

Hello :
the sum is arithmetic secquence of common -diff is :
(-7)-(-5) =(-5)-(-3) = (-3)-(-1) =-2 = d
the first term is : a1 = -1
<span>the formula of the sum : S= (n/2)(a1 +an)
n is number of term an = a1+(n-1)d</span>

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