> 数学 >
已知x+y=9,xy=20,求
y+1
x+1
+
x+1
y+1
的值.
人气:269 ℃ 时间:2020-09-29 05:35:23
解答
∵x+y=9,xy=20,
∴原式=
(y+1)2+(x+1)2
(x+1)(y+1)

=
y2+2y+1+x2+2x+1
xy+x+y+1

=
(x+y)2−2xy+2(x+y)+2
xy+(x+y)+1

=
81−40+18+2
20+9+1

=
61
30
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