Tính các tổng dưới đây sau khi đã rút gọn phân số
a) \(\frac{{ - 3}}{{29}} + \frac{{16}}{{58}}\)
b) \(\frac{8}{{40}} + \frac{{ - 36}}{{45}}\)
c) \(\frac{{ - 8}}{{18}} + \frac{{ - 15}}{{27}}\)
Câu a
\(\begin{array}{l}
\frac{{ - 3}}{{29}} + \frac{{16}}{{58}} = \frac{{ - 3}}{{29}} + \frac{8}{{29}}\\
= \frac{{ - 3 + 8}}{{29}} = \frac{5}{{29}}
\end{array}\)
Câu b
\(\begin{array}{l}
\frac{8}{{40}} + \frac{{ - 36}}{{45}} = \frac{1}{5} + \frac{{ - 4}}{5}\\
= \frac{{1 + \left( { - 4} \right)}}{5} = \frac{{ - 3}}{5}
\end{array}\)
Câu c
\(\begin{array}{l}
\frac{{ - 8}}{{18}} + \frac{{ - 15}}{{27}} = \frac{{ - 4}}{9} + \frac{{ - 5}}{9}\\
= \frac{{ - 4 + \left( { - 5} \right)}}{9} = \frac{{ - 9}}{9} = - 1
\end{array}\)
-- Mod Toán 6
Copyright © 2021 HOCTAP247