Adding and subtracting functions f (n ) = −2n^3 + 3n^2g(n) = −2n − 4 Find f (n )+ g(n)

For the rule of 78, for a 12-month period, the last term in the sequence is 12 and the series sums to 78. for an 10 month period, the last term is and the series sum is . for a 15 month period, the last term is and the series sum is . for a 20 month period, the last term is and the series sum is