问题 解答题
利用方差公式解方程:
x
+
y-1
+
z-2
=
1
2
(x+y+z)

(注:
.
x
=
1
n
(x1+x2+…+xn)
s2=
1
n
[(x1-
.
x
)2+(x2-
.
x
)2+…+(xn-
.
x
)2]
=
1
n
[(
x21
+
x22
+…+
x2n
)-n(
.
x
)2]
答案

x
=m,
y-1
=n,
z-2
=p.

则x=m2,y=n2+1,z=p2+2.

∴原方程可以变化为:m+n+p=

1
2
(m2+n2+1+p2+2)

即m2+n2+p2-2m-2n-2p+3=0

∴(m-1)2+(n-1)2+(p-1)2=0

∴m=1,n=1,p=1

x
=1,
y-1
=1,
z-2
=1.

∴x=1,y=2,z=3.

单项选择题
单项选择题