An arithmetic series is 2,5,8,11... What is the nth term of this sequence?

Step 1: Difference between each term is 3. As the difference is constant it means that the degree of n in the nth term formula must be 1 (i.e no n^2, n^3 etc.). As we are adding 3 to each successive term we have 3n in the formula.
Step 2: Using a trick, if a 0th term existed it would be 2-3 = -1. Hence the formula is 3n-1.Alternatively, you can substitute in values for n. For the first term i.e n=1, we have 2 = 3(1) - x where x is a constant. Solving for x we get x = 1. It is good practice to use the trick and check your answer by plugging in a couple different values for n, making sure you get the correct term in the sequence