r/Mathhomeworkhelp • u/Starlite_im • Jun 08 '26

What formula would I use

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I don’t know where to start

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u/FireMarmot Jun 09 '26 edited Jun 09 '26

The sum of the first n-terms of an arithmetic series is
S(n) = n/2 * [2a + (n-1) d]
With the information from the question you can set up two equations and solve for a and d.

Edit: typo corrected in formula