Question 934335
In this case, the first term is a1 = -5 and the common difference is d = 4 (eg: -1 minus -5 = 4)

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Sn = n*(a1 + an)/2


Sn = n*(a1 + a1 + d*(n-1))/2


Sn = n*(2a1 + d*(n-1))/2


Sn = n*(2*(-5) + 4*(n-1))/2


S17 = 17*(2*(-5) + 4*(17-1))/2


S17 = 459

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