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Find the sum of the given arithmetic series. 27 + 20 + 13 + 6 + ... + (–36) a. –45 c. 315 b. –9 d. –90
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Find the sum of the given arithmetic series. 27 + 20 + 13 + 6 + ... + (–36) a. –45 c. 315 b. –9 d. –90

User Florian Salihovic
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r=20-27=-7 \\ \\ a_(1)=27 \\ \\ a_(n)=a_(1)+(n-1)r \\ \\ -36=27+(n-1)*(-7) \\ \\ -7(n-1)=-63 \\ \\ n-1=9 \\ \\ n=10 \\ \\ S_(10)= (27-36)/(2)*10=-9*5=-45

\\\ Ben
User Punit Rathore
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