質問: 3n - 2 ================================================================================================================================
回答: The first four terms are #a_1=1# #a_2=4# #a_3=7# #a_4=10# Common difference is #d=3# #### Explanation: #a_n=3n-2# #n=1# #a_1=3x1-2=3-2=1# #n=2# #a_2=3x2-2=6-2=4# #n=3# #a_3=3x3-2=9-2=7# #n=4# #a_4=3x4-2=12-2=10# The first four terms are #a_1=1# #a_2=4# #a_3=7# #a_4=10# Common difference is #a_2-a_1=4-1=3# #a_3-a_2=7-4=3# #a_4-a_3=10-7=3# #d=3#