79(x^9)
x^(3m/2n)
8/27
(ab)²
9a^4过程嘞~~~~~~~~~~~~~~~~~~不好意思第二道写错了2*x^9-4*x^9+81*x^9=79(x^9)x^(3m)/(x^(n+2)*x^(n-2))=x^(3m)/x^(2n)=x^(3m-2n)(-2/3)^6/(2/3)^3=(-1)^6*(2/3)^3=8/27(ab)^4/(ab^2)=(ab)^2(-3)^2*a^4