if a(subn)=2n^2 +n give a simplified algebraic expession in term of k for a(sub k-1). so far i kno...?

Question

its increasing by 2 so is it a(sub k-1) +2?

Answer 1

Isn't it just by replacing all the 'n' in 2n^2+n by 'k-1' and simplify?
a(sub k-1) = 2(k-1)^2 + (k-1)
= 2(k^2-2k+1) + k-1
= 2k^2 - 4k + 2 + k -1
= 2k^2 - 3k + 1