1.x^(2n)=7
原式=9x^(6n)-13x^(4n)=9[x^(2n)]^3-13[x^(2n)]^2=9*7^3-13*7^2=7^2(9*7-13)
=49(63-13)=49*50=2450
2.原式=3^(4m)/3^n=(9^m)^2/3^n=6^2/8=36/8=9/2
3.原式=x^m*x^(3n)/[x^(m-1)*2*x(n-1)]=1/2*x^(m+3n-m+1-n+1)
=1/2x^(2n+2)
4.原式=(a-b)^(m+3)*(a-b)^2*(a-b)^m*[-(a-b)^5]=-(a-b)^(m+3+2+m+5)=-(a-b)^(2m+10)
5.原式=1/4a^2b^4c^2*[-1/3a^3b^3c^6]*12a^3b
=-a^(2+3+3)b^(4+3+1)c^(2+6)
=-a^8b^8c^8
=-(abc)^8