Bài tập về thực hiện phép tính cộng, trừ

1.

a) $\frac{5}{11}+\frac{23}{29}-\frac{16}{11}$

 = $\left ( \frac{5}{11}-\frac{16}{11} \right )+\frac{23}{29}$

 = $-1 +\frac{23}{29}$

 = $\frac{-29}{29}+\frac{23}{29}$

 = $\frac{-6}{29}$

b) $13\frac{2}{5}+\frac{15}{23}+1\frac{6}{10}$

 = $(13 + 1)+\left ( \frac{2}{5}+\frac{15}{23}+\frac{6}{10} \right )$

 = $14 + \left ( \frac{92}{230}+\frac{150}{230}+\frac{138}{230} \right )$

 = $14+\frac{38}{23}$

 = $15\frac{15}{23}$

c) $\frac{2}{5}-\left ( \frac{-2}{7} \right )-\frac{14}{10}$

 = $\left ( \frac{2}{5}-\frac{14}{10} \right )+\frac{2}{7}$

 = $\left ( \frac{4}{10}-\frac{14}{10} \right )+\frac{2}{7}$

 = $-1+\frac{2}{7}$

 = $\frac{-5}{7}$

2. 

a) P = $\frac{2}{3}-\left ( -\frac{1}{4} \right )+\frac{3}{5}-\frac{7}{45}-\left ( -\frac{5}{9} \right )+\frac{1}{12}+\frac{1}{35}$

     = $\left ( \frac{2}{3}+\frac{1}{4}+\frac{1}{12} \right )+\left ( \frac{3}{5}+\frac{5}{9}-\frac{7}{45} \right ) + \frac{1}{35}$

     = $1 + 1 + \frac{1}{35}$

     = $2\frac{1}{35}$

b) Q = $\left ( 5-\frac{3}{4}+\frac{1}{5} \right ) - \left ( 6+\frac{7}{4}-\frac{8}{5} \right )-\left ( 2-\frac{5}{4}+\frac{16}{5} \right )$

     = $(5-6-2)+\left ( \frac{-3}{4}-\frac{7}{4}+\frac{5}{4} \right )+\left ( \frac{1}{5}+\frac{8}{5}-\frac{16}{5} \right )$

     = $-3-\frac{5}{4}-\frac{7}{5}$

     = $-\left ( 3+1+\frac{1}{4}+1+\frac{2}{5} \right )$

     = $-5\frac{13}{20}$

3. Ví dụ:

a) $\frac{-99}{100}=-1-\frac{-1}{100}=\frac{-101}{100}-\frac{-2}{100}$

b) $5\frac{3}{4}=5-\frac{-3}{4}$