a. \(\frac{7}{9}=\frac{28}{36};\frac{5}{12}=\frac{15}{36}\)

b. \(\frac{4}{8}=\frac{16}{32};\frac{5}{12}\text{ không viết đc}\)

a,7/9=28/36;5/12=15/36

a, Phân số đó là \(\frac{7}{9}=\frac{28}{36}\) và \(\frac{5}{12}=\frac{15}{36}\)

b, Phân số đó là \(\frac{4}{7}=\frac{8}{14}\) và \(\hept{\begin{cases}3=\frac{21}{7}\\3=\frac{42}{14}\end{cases}}\)

a,  Phân số đó là 

$\frac{7}{9}=\frac{28}{36}$ và $\frac{5}{12}=\frac{15}{36}$

b, Phân số đó là $\frac{4}{7}=\frac{8}{14}$ và $\text{hept}\{\begin{array}{c}3=\frac{21}{7}\\ 3=\frac{42}{14}\end{array}$

Ta thấy :

\(6=\frac{6}{1}=\frac{6\times27}{1\times27}=\frac{162}{27}\)

\(\frac{3}{9}=\frac{3\times3}{9\times3}=\frac{9}{27}\)

\(MSC:143\)

\(\dfrac{11}{13}=\dfrac{11\times143:13}{13\times143:13}=\dfrac{121}{143}\)

\(\dfrac{9}{11}=\dfrac{9\times143:11}{11\times143:11}=\dfrac{117}{143}\)

11/13=121/143

9/11=117/143

\(\dfrac{11}{13}=\dfrac{11\times11}{13\times11}=\dfrac{121}{143};\dfrac{9}{11}=\dfrac{9\times13}{11\times13}=\dfrac{117}{143}\)

\(\dfrac{15}{36};\dfrac{14}{36}\)

5/12=15/36

7/18=14/36

\(\dfrac{5}{12}=\dfrac{5\times3}{12\times3}=\dfrac{15}{36};\dfrac{7}{18}=\dfrac{7\times2}{18\times2}=\dfrac{14}{36}\)

15/36; 14/36

15/36; 14/36

15/36 và 14/36

\(\dfrac{\dfrac{180}{7}}{36};\dfrac{14}{36}\)

15/36; 14/36

5/12=5*3/12*3=15/36;7/18=7*2/18*2=14/36

        d/s:15/36;;14/36

15/36 & 14/36

a \(\dfrac{5}{7};\dfrac{28}{7}\)

b \(\dfrac{27}{33};\dfrac{165}{33}\)

c \(\dfrac{16}{36};\dfrac{21}{36}\)