x²-4y²分之x²+4x+4乘以3x²+6xy分之x+2
=(x+2)^2/(x+2y)(x-2y)*(x+2)/3x(x+2y)
=(x+2)^3/[3x(x+2y)^2(x-2y)]
是不是分子和分母反了?