Justify whether it is true to say that the following are the nth terms of an AP.

Put n = 1, 2, 3, 4


We get


a1 = 3(1)2 + 5 = 8


a2 = 3(2)2 + 5 = 17


a3 = 3(3)2 + 5 = 32


a4 = 3(4)2 + 5 = 53


List of AP is 8, 17, 32, 53. . . .


a2 - a1 = 17 - 8 = 9


a3 - a2 = 32 - 17 = 15


As


a3 - a2 is not equal to a2 - a1


the list is not an AP


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