1.3x^2+5xy-2y^2+x+9y-42.(x^2+3x+2)(x^2+7x+12)-1203.xy(xy+1)+(xy+3)-2(x+y+1/2)-(x+y-1)^2
热心网友
1)3x^2+5xy-2y^2+x+9y-4=3x^2+(5y+1)x-(2y^2-9y+4)[2y-9y+4=(2y-1)(y-4)]=3x^2+[3(2y-1)-(y-4)]x+3(2y-1)[-(y-4)]=(x+2y-1)(3x-y+4)2)(x^2+3x+2)(x^2+7x+12)-120=(x+1)(x+2)(x+3)(x+4)-120=(x^2+5x+4)(x^2+5x+6)-120=(x^2+5x+4)[(x^2+5x+4)+2]-120=(x^2+5x+4)^2+2(x^2+5x+4)-120=(x^2+5x+4-10)(x^2+5x+4+12)=(x^2+5x-6)(x^2+5x+16)=(x-1)(x+6)(x^2+5x+16)3)xy(xy+1)+(xy+3)-2(x+y+1/2)-(x+y-1)^2=x^2y^2+2xy+3-2(x+y)-1-(x+y)^2+2(x+y)-1=(xy+1)^2-(x+y)^2=(xy-x-y+1)(xy+x+y+1)=(x-1)(y-1)(x+1)(y+1)。
热心网友
烦
热心网友
告诉你一个方法，万一做不出来就用求根式然后倒回去万一倒不回去就写个答案．还能捞几分 ．
热心网友
1.3x^2+5xy-2y^2+x+9y-4=(x+2y-1)(3x-y+4)2.(x^2+3x+2)(x^2+7x+12)-120=(x-1)(x+6)(x^2+5x+16)3.xy(xy+1)+(xy+3)-2(x+y+1/2)-(x+y-1)^2=(x-1)(x+1)(y-1)(y+1)