If the expansion of (x + MX + 8) (x-3x + n) does not contain x ^ 3 term and the constant term is 64, find the value of M, n

If the expansion of (x + MX + 8) (x-3x + n) does not contain x ^ 3 term and the constant term is 64, find the value of M, n

(x ^ 2 + MX + 8) (x ^ 2-3x + n) = x ^ 4 + (M-3) x ^ 3 + (n-3m + 8) x ^ 2 + (mn-24) x + 8N expansion does not contain x ^ 3 term, that is, M-3 = 0, M = 3, constant term is 64, that is, 8N = 64, n = 8