Question

麻烦大家帮我看看这道数学题！！！

(1)
(-8)+10+2+(-1)
=2+2+(-1)
=4+(-1)
=3
(2)
5+(-6)+3+9+(-4)+(-7)
=(-1)+3+9+(-4)+(-7)
=2+9+(-4)+(-7)
=11+(-4)+(-7)
=7+(-7)
=0
(3)
(-0.8)+1.2+(-0.7)+(-2.1)+0.8+3.5
=0.4+(-0.7)+(-2.1)+0.8+3.5
=(-0.3)+(-2.1)+0.8+3.5
=(-0.09)+0.8+3.5
=4.12
(4)
2/1+(-3/2)+5/4+(-2/1)+(-3/1)
=30/15+(-30/20)+30/24+(-30/15)+(-30/10)
=(-30/5)+30/24+(-30/15)+(-30/10)
=30/19+(-30/15)+(-30/10)
=30/4+(-30/10)
=-30/6
大家看我做的对么！

Answer 1

(-0.8)+1.2+(-0.7)+(-2.1)+0.8+3.5
=0.4+(-0.7)+(-2.1)+0.8+3.5
=(-0.3)+(-2.1)+0.8+3.5
=(-0.09)+0.8+3.5
=4.12 这个不对应该是
(-0.8)+1.2+(-0.7)+(-2.1)+0.8+3.5
=0.4+(-0.7)+(-2.1)+0.8+3.5
=(-0.3)+(-2.1)+0.8+3.5
=(-2.4)+0.8+3.5
=(-1.6)+3.5
=1.9
2/1+(-3/2)+5/4+(-2/1)+(-3/1)
=30/15+(-30/20)+30/24+(-30/15)+(-30/10)
=(-30/5)+30/24+(-30/15)+(-30/10)
=30/19+(-30/15)+(-30/10)
=30/4+(-30/10)
=-30/6
这个也不对，第二步就错了,其实这道题可以通过移项解决
2/1+(-3/2)+5/4+(-2/1)+(-3/1)
=2/1+(-2/1)+(-3/2)+(-3/1)+5/4
=0+(-3/2)+(-6/2)+5/4
=(-9/2)+5/4
=(-18/4)+5/4
=-13/4

Answer 2

第（1）（2）对了
第（3）（4）错了
(3)
(-0.8)+1.2+(-0.7)+(-2.1)+0.8+3.5
=0.4+(-0.7)+(-2.1)+0.8+3.5
=(-0.3)+(-2.1)+0.8+3.5
=(-2.4)+0.8+3.5
=(-1.6)+3.5
=1.9

(4)
2/1+(-3/2)+5/4+(-2/1)+(-3/1)
=30/15+(-30/20)+30/24+(-30/15)+(-30/10)
=(-30/5)+30/24+(-30/15)+(-30/10)
=30/19+(-30/15)+(-30/10)
=30/4+(-30/10)
=-30/6
=-5/1

Answer 3

(-0.8)+1.2+(-0.7)+(-2.1)+0.8+3.5
=0.4+(-0.7)+(-2.1)+0.8+3.5
=(-0.3)+(-2.1)+0.8+3.5
=(-2.4)+0.8+3.5
=1.9

2/1+(-3/2)+5/4+(-2/1)+(-3/1)
=2/1-3/2+5/4-2/1-3/1
=2/1-2/1-3/2-3/1+5/4
=0-3/2-3/1+5/4
=-6/4-12/4+5/4
=-13/4

Answer 4

对了`诶```