f(n+1)=f(n)-2 is the recursive function for this arithmetic sequence. The explicit form is:
f(n)=a-d(n-1) where a(initial term) is 10 and d(common difference) is -2
f(n)=10-2(n-1) which cleans up to
f(n)=12-2n so the first few terms are:
10,8,6,4,2,0,-2,-4.....
