[tex]-3x^3y^2(-4x^2 \underbrace{y\cdot y\cdot y\cdot y}_{y^4})^2\\\\=(-3)(-4)(x^3x^2)(y^2y^4)\\\\=12x^{3+2}y^{2+4}\\\\=\boxed{12x^5y^6}\\\\Used:\\\\a^n\cdot a^m=a^{n+m}[/tex]
It is 12x^5 y^6 hope it helps
