^ 表示乘方
(1)：原式=(xy^4)^m
=(x^m)×y^(4×m)
=(x^m)y^4m
(2)：原式=-(p²q)^n
=-(p^2n)×q^n
=-(p^2n)q^n
(3)：原式=(xy^3n)²+(xy^6)^n
=x²y^(3n×2)+(x^n)×y^(6×n)
=x²y^(6n)+(x^n)y^6n
=(x²+x^n)y^6n