一、判断题（运用加法运算律判断下列各式变形是否正确，正确打“√”，错误打“×”）
（）1. $(+3)+(-8)+(+7)+(-2) = [(-8)+(-2)] + [(+3)+7]$.
（）2. $(-1.8)+(+0.7)+1.3+(-0.2) = [(-1.8)+(-0.2)] + [0.7+1.3]$.
（）3. $(-\dfrac{1}{6})+\dfrac{1}{12}+(-\dfrac{3}{4})+\dfrac{2}{3} = [(-\dfrac{1}{6})+\dfrac{2}{3}] + [\dfrac{1}{12} + (-\dfrac{3}{4})]$.
（）4. $(-1\dfrac{2}{3})+\dfrac{1}{2}+(-\dfrac{1}{3})+(-8\dfrac{1}{2}) = [(-1\dfrac{2}{3})+(-\dfrac{1}{3})] + [\dfrac{1}{2} + (-8\dfrac{1}{2})]$.
（）5. $-1\dfrac{5}{6} + (-5\dfrac{2}{3})+4\dfrac{3}{4} = (-1 - \dfrac{5}{6})+(-5 - \dfrac{2}{3})+(4 + \dfrac{3}{4}) = [(-1)+(-5)+4] + [(-\dfrac{5}{6})+(-\dfrac{2}{3})+\dfrac{3}{4}]$.

1. √ 2. √ 3. √ 4. √ 5. √

6. $16 + (-3) + (-5) + 2.$

6. 10

7. $(-4)+(+13)+(-5)+(-9)+7.$
8. $(-4.3)+2.5+(-5.7)+(-7.5).$
9. $1\frac{3}{4}+(+\frac{5}{8})+(-0.75)+\frac{3}{8}.$
10. $(-2\frac{4}{5})+(+3.5)+(-1\frac{1}{5})+(-2\frac{1}{2}).$
11. $-4\frac{1}{8}+(-5\frac{1}{2})+(+0.125)+3\frac{1}{2}.$
12. $(-\frac{3}{4})+3\frac{3}{8}+(-5\frac{1}{2})+\left|-2\frac{5}{8}\right|.$

7. 2 8. -15 9. 2 10. -3 11. -6 12. $-\dfrac{1}{4}$