已知x的2n次方=3,y的3m次方=2,求代数式2x的6n次方-(x的n次方)的平方乘y的m次方,乘x的2n次方乘

x^2n=3
y^3m=2
2x^6n-(x^n)^2*y^m*x^2n*(y^2)^m-y^9m
=2*(x^2n)^3-x^2n*y^m*x^2n*y^2m-y^9m
=2*(x^2n)^3-x^2n*x^2n*y^2m*y^m-y^9m
=2*(x^2n)^3-x^2n*x^2n*y^3m-(y^3m)^3
=2*3-3*3*2-2^3
=6-18-8
=-20