(adsbygoogle = window.adsbygoogle || []).push({}); i need help- arithmetic sequences

There many arithmetic sequences which seventh term equals 5. prove all of them have the same sum of their first 13 elemnets. find the sum

i found the sum was 65 but i dont know how to prove it.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Arithmetic sequences

**Physics Forums | Science Articles, Homework Help, Discussion**