问题
解答题
已知x+y=12,xy=9,且x<y.求
|
答案
由已知x+y=12,xy=9,且x<y,可得 (x-y)2=(x+y)2-4xy=144-36=108,∴x-y=-6
.3
∴
=x
-y1 2 1 2 x
+y1 2 1 2
=(x
-y1 2
)21 2 x-y
=(x+y)-2(xy) 1 2 x-y
=-12-2×9 1 2 -6 3
.3 3
已知x+y=12,xy=9,且x<y.求
|
由已知x+y=12,xy=9,且x<y,可得 (x-y)2=(x+y)2-4xy=144-36=108,∴x-y=-6
.3
∴
=x
-y1 2 1 2 x
+y1 2 1 2
=(x
-y1 2
)21 2 x-y
=(x+y)-2(xy) 1 2 x-y
=-12-2×9 1 2 -6 3
.3 3