$\begin{array}{|c|}\hline{\text{Đ}}\\{\text{S}}\\\hline\end{array}?$

a) $\dfrac{4}{9}+\dfrac{1}{2}=\dfrac{17}{18}$

b) $\dfrac{7}{8}-\dfrac{5}{6}=\dfrac{1}{2}$

c) $3-\dfrac{3}{4}=\dfrac{6}{4}$

d) $2-\dfrac{4}{5}=\dfrac{6}{5}$

a)

$\frac{4}{9}$ + $\frac{1}{2}$

= $\frac{8}{18}$ + $\frac{9}{18}$

= $\frac{17}{18}$

⇒ $\frac{4}{9}$ + $\frac{1}{2}$ = $\frac{17}{18}$ là ĐÚNG

b)

$\frac{7}{8}$ - $\frac{5}{6}$

= $\frac{21}{24}$ - $\frac{16}{24}$

= $\frac{5}{24}$ 

 ⇒ $\frac{7}{8}$ - $\frac{5}{6}$ = $\frac{1}{2}$  là SAI

c)

3 - $\frac{3}{4}$

= $\frac{12}{4}$ - $\frac{3}{4}$

= $\frac{9}{4}$ 

 ⇒ 3 - $\frac{3}{4}$ = $\frac{6}{4}$  là SAI

d)

2 - $\frac{4}{5}$

= $\frac{10}{5}$ - $\frac{4}{5}$

= $\frac{6}{5}$ 

 ⇒ 2 - $\frac{4}{5}$ = $\frac{6}{5}$   là ĐÚNG

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