6xy+9x^2-m^2+y^2=（3x+y)²-m²=(3x+y+m)(3x+y-m)x^2·y-4y(x+y)^2=y*[x²-4(x+y)²]=y(x-2x-2y)(x+2x+2y)=-y(x+2y)(3x+2y) a^2+4b+b^2-2a+5=0,求a,ba²-2a+1+b²+4b+4=0(a-1)+(b+2)...