题目内容
下面计算错在哪一步?如果错误,请指出错误之处,并写出正确答案.
(+1
)-(+
)-(-
)-(+1
)
=1
-
+
-1
①
=(1
+
)-(
-1
)②
=2-(-
)③
=2+
=2
.
(+1
4 |
5 |
2 |
3 |
1 |
5 |
1 |
3 |
=1
4 |
5 |
2 |
3 |
1 |
5 |
1 |
3 |
=(1
4 |
5 |
1 |
5 |
2 |
3 |
1 |
3 |
=2-(-
2 |
3 |
=2+
2 |
3 |
2 |
3 |
分析:根据有理数的减法运算法则判断出②错误,然后进行计算即可得解.
解答:解:错在②的第二个括号内的运算.
正确解答为:(+1
)-(+
)-(-
)-(+1
)
=1
-
+
-1
=(1
+
)-(
+1
)
=2-2
=0.
正确解答为:(+1
4 |
5 |
2 |
3 |
1 |
5 |
1 |
3 |
=1
4 |
5 |
2 |
3 |
1 |
5 |
1 |
3 |
=(1
4 |
5 |
1 |
5 |
2 |
3 |
1 |
3 |
=2-2
=0.
点评:本题考查了有理数的减法,熟记减去一个数等于加上这个数的相反数是解题的关键.
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