a.Ta thấy:\(\frac{3}{4}=\frac{3.9}{4.9}=\frac{27}{36}\)

\(\Rightarrow\frac{3}{4}=\frac{27}{36}\)

b.ta thấy:\(\frac{-4}{5}=\frac{-4.9}{5.9}=\frac{-36}{45};\frac{8}{-9}=\frac{8.\left(-5\right)}{-9.\left(-5\right)}=\frac{-40}{45}\)

Vì\(\frac{-36}{45}>\frac{-40}{45}\)nên\(\frac{-4}{5}\)ko bằng\(\frac{8}{-9}\)

c.Ta thấy:\(\frac{10}{14}=\frac{5}{7};\frac{-15}{-21}=\frac{5}{7}\)

\(\Rightarrow\frac{10}{14}=\frac{-15}{-21}\)

chúc bn hok tốt!!!

nhớ k mk nha!!!!

nếu được thì kb luôn nha!!!

 \(\dfrac{143}{363}\) = \(\dfrac{143:11}{363:11}\) = \(\dfrac{13}{33}\) (đpcm)

\(\dfrac{1212}{2727}\) = \(\dfrac{1212:101}{2727:101}\) = \(\dfrac{12}{27}\) (đpcm)

\(\dfrac{13}{33}\)  và \(\dfrac{143}{363}\)

\(\dfrac{13}{33}=\dfrac{13\times11}{33\times11}=\dfrac{143}{363}\)

\(\dfrac{143}{363}=\dfrac{143\times1}{363\times1}=\dfrac{143}{363}\)

\(\dfrac{1212}{2727}\)  và \(\dfrac{12}{27}\)

\(\dfrac{12}{27}=\dfrac{12\times101}{27\times101}=\dfrac{1212}{2727}\)

\(\dfrac{1212}{2727}=\dfrac{1212\times1}{2727\times1}=\dfrac{1212}{2727}\)

đó là toán mà

\(39+\dfrac{13}{84}+57=\dfrac{8077}{84}\)

\(78+\dfrac{26}{168}+114=\dfrac{16141}{84}\)

-24/42=-4/7

-24/36=-2/3

-8/56=-1/7

29/-87=-1/3

51/-18=-17/3