题目内容
(2012?河池模拟)求未知数X的值.
(X+12)×
=42-X
2
÷(X-0﹒55)=
6.5:X=
:75%
(X+12)×
2 |
5 |
2
1 |
7 |
32 |
7 |
6.5:X=
3 |
8 |
分析:(1)把原式变为
X+
=42-X,根据等式的性质,两边同减去
,得
X=
-X;两边同加上X,得
X=
,两边同乘
即可;
(2)根据等式的性质,两边同乘(X-0.55),得
×(X-0.55)=
;两边同乘
,得X-0.55=
,两边同加上0.55即可;
(3)先根据比例的性质改写成
X=6.5×75%,再根据等式的性质,两边同乘
即可.
2 |
5 |
24 |
5 |
24 |
5 |
2 |
5 |
186 |
5 |
7 |
5 |
186 |
5 |
5 |
7 |
(2)根据等式的性质,两边同乘(X-0.55),得
32 |
7 |
15 |
7 |
7 |
32 |
15 |
32 |
(3)先根据比例的性质改写成
3 |
8 |
8 |
3 |
解答:解:(1)(X+12)×
=42-X,
X+12×
=42-X,
X+
=42-X,
X+
-
=42-X-
,
X=
-X,
X+X=
-X+X,
X=
,
X×
=
×
,
X=
;
(2)2
÷(X-0﹒55)=
,
2
÷(X-0﹒55)×(X-0.55)=
×(X-0.55),
×(X-0.55)=
,
×(X-0.55)×
=
×
,
X-0.55=
,
X-0.55+0.55=0.46875+0.55,
X=1.01875;
(3)6.5:X=
:75%,
X=6.5×75%,
X=
×
,
X=
,
X×
=
×
,
X=13.
2 |
5 |
2 |
5 |
2 |
5 |
2 |
5 |
24 |
5 |
2 |
5 |
24 |
5 |
24 |
5 |
24 |
5 |
2 |
5 |
186 |
5 |
2 |
5 |
186 |
5 |
7 |
5 |
186 |
5 |
7 |
5 |
5 |
7 |
186 |
5 |
5 |
7 |
X=
186 |
7 |
(2)2
1 |
7 |
32 |
7 |
2
1 |
7 |
32 |
7 |
32 |
7 |
15 |
7 |
32 |
7 |
7 |
32 |
15 |
7 |
7 |
32 |
X-0.55=
15 |
32 |
X-0.55+0.55=0.46875+0.55,
X=1.01875;
(3)6.5:X=
3 |
8 |
3 |
8 |
3 |
8 |
13 |
2 |
3 |
4 |
3 |
8 |
39 |
8 |
3 |
8 |
8 |
3 |
39 |
8 |
8 |
3 |
X=13.
点评:此题考查了根据等式的性质解方程,即等式两边同加、同减、同乘或同除以一个数(0除外),等式的左右两边仍相等;注意等号上下要对齐.
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