Question

find s25 for the following arithmetic sequence -7, -2, 3, 8,...

Answer 1

What is the pattern?

Answer 2

You need to find the difference (d) between the terms. Once you have that you can use the formula, \[a_n=a_1+d(n-1)\]
Where n is the number term, d is the difference between terms, a_1 is the first term in the series, and a_n is the value of the term you're looking for.