Question

已知x+y=4，xy=-12，则(x加1分之y加1)加(y加1分之x加1) 网上答案有错误,请求高手亲自帮忙解答,谢谢

还有这题,x加y等于负4,xy=-12，则(x加1分之y加1)加(y加1分之x加1)等于什么,谢谢

Answer 1

由x+y=4，xy=-12可得x=6,y=-2或x=-2,y=6.将这两组数据分别代入该式（y+1）/（x+1）+（x+1）/（y+1）=-50/7，两组得到的都一样哦

Answer 2

(y+1)/(x+1)+(x+1)/(y+1)
=(y+1)^2/[(x+1)(y+1)]+(x+1)^2/[(x+1)(y+1)]
=[(y+1)^2+(x+1)^2]/[(x+1)(y+1)]
=[y^2+2y+1+x^2+2x+1]/[x(y+1)+(y+1)]
=[y^2+x^2+2x+2y+2]/[xy+x+y+1]
=[y^2+x^2+2(x+y)+2]/[-12+4+1]
=[y^2+x^2+2*4+2]/[-7]
=[y^2+x^2+10]/[-7]
=[y^2+x^2-2*12+24+10]/[-7]
=[y^2+x^2+2xy+34]/[-7]
=[(x+y)^2+34]/(-7)
=[4^2+34)/(-7)
=(16+34)/(-7)
=-50/7

Answer 3

先解出x和y，x,y一个等于6一个等于-2，不管哪个是，问题是对称的,随便带一种情况都行,x=-2,y=6，就可以算出来了,等于48/7.