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katiebugg
 3 years ago
The third term of an arithmetic sequence is 9 and the seventh term is 31. Find the sum of the first twentytwo terms.
katiebugg
 3 years ago
The third term of an arithmetic sequence is 9 and the seventh term is 31. Find the sum of the first twentytwo terms.

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helder_edwin
 3 years ago
Best ResponseYou've already chosen the best response.0an arithmetic sequence is of the form \[ \large a_1\qquad\text{not given} \] \[ \large a_2=a_1+d \] \[ \large 9=a_3=a_2+d=a_1+2d \] so \[ \large 31=a_7=a_1+6d \]

helder_edwin
 3 years ago
Best ResponseYou've already chosen the best response.0u end up with \[ \large 9=a_1+2d \] \[ \large 31=a_1+6d \] solve this system

helder_edwin
 3 years ago
Best ResponseYou've already chosen the best response.0r u there @katiebugg ?

katiebugg
 3 years ago
Best ResponseYou've already chosen the best response.0sorry yeahh was working on a prob thanks!!!
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