1. \(3x\left(x^2+2y\right)^2-12xy\left(x^2+y\right)\)\(=3x\left(x^4+4x^2y+4y^2\right)-12x^3y-12xy^2\)
\(=3x^5+12x^3y+12xy^2-12x^3y-12xy^2=3x^5\)
2. \(u^2v^2\left(u+v\right)^2-\left(u^2v+uv^2\right)^2\)
\(=u^2v^2\left(u^2+2uv+v^2\right)-\left(u^4v^2+2u^3v^3+u^2v^4\right)\)
\(=u^4v^2+2u^3v^3+u^2v^4-u^4v^2-2u^3v^3-u^2v^4=0\)