Question

Find an explicit formula for the arithmetic sequence -11,-3,5,13,...

Answer 1

tn=-11+8(n-1). n represents which number of the sequence you will find, so if you plugged in a 3 you would find the third number in the sequence. 

Answer 2

In this sequence, a1 = -11, k = 8

So an = a1 + (n-1)k = -11 + (n-1)*8 = 8n - 19