x^2+2xy+y^2+3x+3y-4=(x+y)^2+3(x+y)-4完全平方公式加提取公因式=(x+y+4)(x+y-1) 十字相乘法希望有所帮助望采纳，谢谢
x^2+2xy+y^2+3x+3y-4=(x+y)^2+3(x+y)-4=(x+y+4)(x+y-1)
