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1
.下列各式中,计算结果是
x
2
+
7x
-
18
的是
(
)
A
.
(x
-
1)(x
+
18) B
.
(x
+
2)(x
+
9)
C
.
(x
-
3)(x
+
6) D
.
(x
-
2)(x
+
9)
D
2
.计算
(3a
+
2)(4a
2
-
a
-
1)
的结果中二次项系数是
(
)
A
.-
3 B
.
8 C
.
5 D
.-
5
C
3
.若
(x
+
1)(2x
-
3)
=
2x
2
+
mx
+
n
,则
m
=
________
,
n
=
________
.
-
1
-
3
4
.计算下列各题:
(1)(6x
-
y)(6x
+
y)
;
(2)2(x
-
2)(x
+
3)
-
5(x
-
3)(x
+
8)
.
(1)36
x
2
-
y
2
(2)
-
3
x
2
-
23
x
+
108
5
.解方程:
(x
+
7)(x
+
5)
-
(x
+
1)(x
+
5)
=
42.
x
=
2