.
2
Give
:
E(X)
2
=
E(X)
,
for (X y)
p(X y)
=
,
-1
=
.
,
p(x Y)
=
rx
4
=
Var(y)
,
=
9
p(X y)
,
,
my
Var(Y)
·
Find Var(2X-34)
Var(ax + bY)
·
Therefore
a
,
=
2
Var(x)
b
,
=
Var(x)
=
4
,
lov(x Y)
=
:
Var(2x
=
16
We'll
y(3)
use the
We know
identity
=
Var (X -Y)
=
z
=
=
:
E((X
-
y(z)
=
=
9
=
+
81
+
=
I
( 3)(q)
-
+
2(z)( 3)(i)
-
12
-
E((X-2)
,
E(X -y)
,
,
E
=
-
b Var(y) + zab for (X Y)
3
2(n)
=
=
Find E((X
+
a
t ..
=
3y)
=
Var(y)
,
(1)
-
Var(x)
·
,
a)
Var(x)
,
11
-
(
-
1)
=
=
Var(X -y)
+
+ 9
11
+
32
20
-
(E(X
3
Var(x) Var(y)
4
+
-
2()
-
2 hor (X Y)
,
-
y))
=
-