x^4+4x^3+4x^2 -9= x^2(x^2+4x+4) -9= x^2(x+2)^2 -9= [x(x+2)]^2 -9= (x^2+2x)^2 -9= (x^2+2x+3)(x^2+2x-3)= (x^2+2x+3)(x+3)(x-1)--------------------梳理知识,帮助别人,愉悦自己.“数理无限”团队欢迎你...