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©2026 数学クラブ http://sugaku.club/
月 日( )
● 次の方程式を解きなさい
[225-00]
(1)
2
x
+
7
x
+
5
=
−3
x
−
20
(2)
2
x
−
10
x
+
10
=
−21
x
−
8
(3)
2
x
+
4
x
−
9
=
x
+
45
(4)
(
x
−
7
)
(
x
+
4
)
=
5
(
−3
x
−
11
)
(5)
2
x
+
7
x
+
7
=
14
x
+
25
©2026 数学クラブ http://sugaku.club/
月 日( )
【解答例】
(1)
2
x
+
7
x
+
5
=
−3
x
−
20
2
x
+
10
x
+
25
=
0
2
(
x
+
5
)
=
0
x
=
−5
(2)
2
x
−
10
x
+
10
=
−21
x
−
8
2
x
+
11
x
+
18
=
0
(
x
+
9
)
(
x
+
2
)
=
0
x
=
−9
,
−2
(3)
2
x
+
4
x
−
9
=
x
+
45
2
x
+
3
x
−
54
=
0
(
x
+
9
)
(
x
−
6
)
=
0
x
=
−9
,
6
(4)
(
x
−
7
)
(
x
+
4
)
=
5
(
−3
x
−
11
)
2
x
−
3
x
−
28
=
−15
x
−
55
2
x
+
12
x
+
27
=
0
(
x
+
9
)
(
x
+
3
)
=
0
x
=
−9
,
−3
(5)
2
x
+
7
x
+
7
=
14
x
+
25
2
x
−
7
x
−
18
=
0
(
x
−
9
)
(
x
+
2
)
=
0
x
=
9
,
−2