x+3y+9y^2/(x-3y)+6x^2y/(9y^2-x^2)＝[(x+3y)(x-3y)+9y²]/(x-3y) + 6x²y/(9y²-x²)=x²/(x-3y) + 6x²y/(9y²-x²)=-x²/(3y-x) + 6x²y/[(3y+x)(3y-x)]=[-x²(3y+x...