初一数学(有理数加减法混合运算)
1.计算(能简算的要简算)写过程(-0.8)+1.2+(-0.7)+(-2.1)+0.8+3.51/2+(-2/3)+4/5+(-1/2)+(-1/3)-4.2+5.7-...
1.计算(能简算的要简算)写过程
(-0.8)+1.2+(-0.7)+(-2.1)+0.8+3.5
1/2+(-2/3)+4/5+(-1/2)+(-1/3)
-4.2+5.7-8.4+10
-1/4+5/6+2/3-1/2 展开
(-0.8)+1.2+(-0.7)+(-2.1)+0.8+3.5
1/2+(-2/3)+4/5+(-1/2)+(-1/3)
-4.2+5.7-8.4+10
-1/4+5/6+2/3-1/2 展开
4个回答
展开全部
(-0.8)+1.2+(-0.7)+(-2.1)+0.8+3.5
=(-0.8+0.8)+(1.2+3.5-0.7)-2.1
=4-2.1
=1.9
1/2+(-2/3)+4/5+(-1/2)+(-1/3)
=(1/2-1/2)+4/5-(2/3+1/3)
=4/5-1
=-1/5
-4.2+5.7-8.4+10
=(5.7+10)-(4.2+8.4)
=15.7-12.6
=3.1
-1/4+5/6+2/3-1/2
=(5/6+2/3)-(1/4+1/2)
=(5/6+4/6)-(1/4+2/4)
=9/6-3/4
=3/2-3/4
=6/4-3/4
=3/4
=(-0.8+0.8)+(1.2+3.5-0.7)-2.1
=4-2.1
=1.9
1/2+(-2/3)+4/5+(-1/2)+(-1/3)
=(1/2-1/2)+4/5-(2/3+1/3)
=4/5-1
=-1/5
-4.2+5.7-8.4+10
=(5.7+10)-(4.2+8.4)
=15.7-12.6
=3.1
-1/4+5/6+2/3-1/2
=(5/6+2/3)-(1/4+1/2)
=(5/6+4/6)-(1/4+2/4)
=9/6-3/4
=3/2-3/4
=6/4-3/4
=3/4
展开全部
首先得知道拆括号的法则:大概就是括号前有加号或没有符号者直接拆;括号前有减号者括号内的符号改成相反的 ,之后就按小学的方法来算。
(-0.8)+1.2+(-0.7)+(-2.1)+0.8+3.5=1.2-0.7+0.8-0.8+3.5-2.1=0.5+1.4=1.9
1/2+(-2/3)+4/5+(-1/2)+(-1/3)=1/2-2/3+4/5-1/2-1/3=1/2-1/2-2/3-1/3+4/5=0-(2/3+1/3)+4/5=4/5-1=-(1-4/5)=-1/5
-4.2+5.7-8.4+10=5.7+10-(4.2+8.4)=15.7-12.6=3.1
-1/4+5/6+2/3-1/2=5/6+2/3-(1/4+1/2)=3/4
(-0.8)+1.2+(-0.7)+(-2.1)+0.8+3.5=1.2-0.7+0.8-0.8+3.5-2.1=0.5+1.4=1.9
1/2+(-2/3)+4/5+(-1/2)+(-1/3)=1/2-2/3+4/5-1/2-1/3=1/2-1/2-2/3-1/3+4/5=0-(2/3+1/3)+4/5=4/5-1=-(1-4/5)=-1/5
-4.2+5.7-8.4+10=5.7+10-(4.2+8.4)=15.7-12.6=3.1
-1/4+5/6+2/3-1/2=5/6+2/3-(1/4+1/2)=3/4
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展开全部
(-0.8)+1.2+(-0.7)+(-2.1)+0.8+3.5
=(1.2+0.8+3.5)-(0.8+0.7+2.1)
=(2+3.5)-(1.5+2.1)
=3.5-1.5+(2-2.1)
=2-0.1
=1.9 此题:所有正数作和,负数也作和,最后整个式子 剩一个正数和一个负数,以使式子计算简化
1/2+(-2/3)+4/5+(-1/2)+(-1/3)
=1/2+(-1/2)+(-2/3)+(-1/3)+4/5
=1/2- 1/2 - 2/3 -1/3 +4/5
=0-1+4/5
=-1/5
-4.2+5.7-8.4+10
=10+5.7-4.2-8.4
=15.7-12.6
=3.1
-1/4+5/6+2/3-1/2
=-1/4 - 1/2 + 5/6 + 2/3
=-1/4 - 2/4 + 5/6 + 4/6 负与负合并,正数与正数合并
=-3/4 + 9/6
=-9/12 + 18/12 化分母相同
=9/12
=3/4
=(1.2+0.8+3.5)-(0.8+0.7+2.1)
=(2+3.5)-(1.5+2.1)
=3.5-1.5+(2-2.1)
=2-0.1
=1.9 此题:所有正数作和,负数也作和,最后整个式子 剩一个正数和一个负数,以使式子计算简化
1/2+(-2/3)+4/5+(-1/2)+(-1/3)
=1/2+(-1/2)+(-2/3)+(-1/3)+4/5
=1/2- 1/2 - 2/3 -1/3 +4/5
=0-1+4/5
=-1/5
-4.2+5.7-8.4+10
=10+5.7-4.2-8.4
=15.7-12.6
=3.1
-1/4+5/6+2/3-1/2
=-1/4 - 1/2 + 5/6 + 2/3
=-1/4 - 2/4 + 5/6 + 4/6 负与负合并,正数与正数合并
=-3/4 + 9/6
=-9/12 + 18/12 化分母相同
=9/12
=3/4
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