Answer:
To find the recursion formula for this sequence, we need to identify the pattern in how each term is related to the previous term. Notice that each term is obtained by adding 10 to the previous term. This means that:a1 = 8 (the first term)
a2 = a1 + 10 = 18
a3 = a2 + 10 = 28
a4 = a3 + 10 = 38So, we can express the nth term in terms of the (n-1)th term using the recursion formula:an = an-1 + 10Therefore, the recursion formula for the sequence 8, 18, 28, 38 is:an = an-1 + 10, where a1 = 8.