How can you find the first term of an arithmetic sequence if you know the third and fifth terms?

Question

misty1212 · Answer

hi!

anonymous · Answer

Find the difference between the 3rd an 5th terms. That difference should be the same difference between the 1st and 3rd terms.

anonymous · Answer

thank you

anonymous · Answer

If the common difference in an arithmetic sequence is 4, and the 20th term is 36, what is the first term? for this do i subtract 4 times 19 from 36?

anonymous · Answer

Yes.

To go back one term, you subtract the common difference of 4. To get to the first term from term 20, you have to back 19 terms. In total, you should go back 4*19 or 76.