Question

The first term of an arithmetic sequence is -5, and the twelfth term is 17. Find the common difference.

Answer 1

$a_1=-5;\ a_{12}=17\\\\a_{12}-a_1=11d\\\\11d=17-(-5)\\\\11d=17+5\\\\11d=22\ \ \ |:11\\\\d=2$

Answer: The common difference is equal 2.