The answer to the proficiency test A:1-8bcaaabc9 is not unique; -7/ 1 1a^bc 10，4 1 1，- 1.5 12，200 13，0.00000526 14, 4a^2+7ab- 15b^2 15,n^3-4n 16,[2n]^2- 1 17，& lt！ & gt，-3x-7 & lt； 2 & gt，7/8y-xz & lt； 3 & gt2ab 18, 1 19, because the coefficients of the items containing the letter x in the calculation results are all 0, so the value of A-B+C has nothing to do with the value of x .. 2 1, 20 kinds.

Level test; 9,x^2y 10， 1 1,a^ 15 12，& gt