已知x+y=5,xy=6,x+2分之1+y+2分之1=?

来源:学生作业帮助网 编辑:作业帮 时间:2024/04/29 20:42:21

已知x+y=5,xy=6,x+2分之1+y+2分之1=?

1/(x+2)+1/(y+2)
=(x+2+y+2)/(x+2)(y+2)
=(x+y+4)/(xy+x+y+4)
=(5+4)/(6+5+4)
=3/5

你这题有歧义,加个括号好吧?

(1/x+2)+(1/y+2)
=(x+y+2+2)/(x+2)(y+2)
=(5+2+2)/(6+5+5+4)
=0.45

6

x+2分之1+y+2分之1
=(x+2)(y+2)分之(y+2)+(x+2)(y+2)分之(x+2)
=(x+2)(y+2)分之(x+y+4)
=(xy+2x+2y+4)分之(x+y+4)
=[xy+2(x+y)+4]分之(x+y+4)
=(6+10+4)分之(5+4)
=20分之9