Find the coefficient of x ^ 5 in (1 + x-x ^ 2) ^ 6 expansion Please explain the process. Thank you The answer is 6

Find the coefficient of x ^ 5 in (1 + x-x ^ 2) ^ 6 expansion Please explain the process. Thank you The answer is 6

Is it permutation
One X two - x2
Three X, one - x2
Five X's
Total = (6 * 10) + (- 6 * 20) + (6) = - 54