3x^3 × x^4 + 2x × x^2 × x^4 - 4x^5 × (-x)^2
=3x^7+2x^7-4x^7
=x^7
(-1)^2x × (-1)^2
=(-1)^(2x+2)
=1
a^3 × (-a)^4
=a^7
-[(m-n)^2]^4
=-(m-n)8
a^2 × (-a)^3 × (-a^2)^3
=a^2 × (-a^3) × (-a^6)
=a^11
[-(-x^2)^3]^3
=(x^6)^3
=x^18
(-a^2)×(-a^3)^3
=(-a^2)×(-a^9)
=a^11