75x^6*y-12x^2*y^5
=x²y/12*(900x^4-144y^4)
=x²y/12*(30x²-12y²)*(30x²+12y²)
=x²y/12*36*(5x²-2y²)*(5x²+2y²)
=3x²y*(5x²-2y²)*(5x²+2y²)