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**flexus** find the partial sum

100

∑ 6*n*

*n*=10

ok this is what i did but i didnt get the same answer as the book can someone tell me what i did wrong please?

100

∑ 6*n*

*n*=10

60+66+72+78+...

a1=60 d=66-60--> d=6

c=a1-d --> c=60-6 --> c= 54

a*n*= d*n*+c --> a*n*= 6n+54 --> a100=6(100)+54 --> a100= 654

Sn= *n/2(a1+an*) --> Sn=100/2(60+654) --> Sn= 35700 which is the wrong answer......aarrrrrrrrrrrrrrrrhhhhh(Headbang)

i looked in the back of the book and the correct answer is 30,030. what did i do wrong?