[(x平方+4x+4)分之(x平方-4y平方)]除以[(3x平方+6xy)分之(x+2)]=[(x²-4y²)/(x²+4x+4)]/[(x+2)/(3x²+6xy)]=[(x+2y)(x-2y)/(x+2)²]/{(x+2)/[3x(x+2y)]}=3x(x+2y)²(x-2y)/(x+2)³...