已知x-y+3=0,求2xy-x^2-y^2+1的值

已知x-y+3=0,求2xy-x^2-y^2+1的值
已知x-y+3=0,求2xy-x^2-y^2+1的值

已知x-y+3=0,求2xy-x^2-y^2+1的值
x－y＝﹣3
2xy－x²－y²＋1
＝﹣﹙x－y﹚²＋1
＝﹣﹙﹣3﹚²＋1
＝﹣9＋1
＝﹣8