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Mathematics 7 Online
OpenStudy (jojokiw3):

How do I solve this series like these?

OpenStudy (jojokiw3):

\[\sum_{k=1}^{425}(9k-3219)\]

rishavraj (rishavraj):

see its forming an arithmetic series

OpenStudy (owikbenstan):

Find the 1st and Last terms using the formula, add them together and divide by 2 (take the average of the first and last terms) then multiply the amount of terms 424 in this case.

rishavraj (rishavraj):

first term -3210 second -3201 third -3192

rishavraj (rishavraj):

@jojokiw3 as @owikbenstan told just plug k = 1 u will get first term and k = 425 u wil get last term and \[S_n = \frac{ n }{ 2 }(a_1 + a_n)\]

OpenStudy (jojokiw3):

-553350

OpenStudy (freckles):

\[\sum_{k=1}^{n} k=\frac{n(n+1)}{2} \\ \sum_{k=1}^{n} c= c \cdot n\] you can also use these

rishavraj (rishavraj):

@jojokiw3 yup @owikbenstan it should be 425

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