note that since for each new term we are adding or subtracting a constant number, we can describe the pattern by an arithmetic sequence.
recall that an arithmetic sequence is one of the form:
where is the nth term, is the first term, is the current number of the term, and is the common difference (that is, the constant we add to one term to get the next term).
fill in the corresponding value in the formula and simplify. the result will be in the form of the equation of a line
an alternative is to use the point-slope form of the equation of a line to find the answer.
the point slope form is: , where is the slope, which we can find from any two points, and is a point the line passes through (in this case, of course, n is the input value, so n would replace x in the formulas)