\(1,\)\(a,\dfrac{2+3}{9+3}=\dfrac{5}{12}\)
\(\Leftrightarrow\dfrac{5}{12}=\dfrac{5.3}{12.3}=\dfrac{15}{36}\) và \(\dfrac{6}{9}=\dfrac{24}{36}\)
\(\dfrac{15}{36}< \dfrac{24}{36}\Rightarrow\dfrac{5}{12}< \dfrac{6}{9}\) hay \(\dfrac{2+3}{9+3}< \dfrac{6}{9}\)
\(\dfrac{2}{3}=\dfrac{8}{12}\Rightarrow\dfrac{5}{12}< \dfrac{2}{3}\) hay \(\dfrac{2+3}{9+3}< \dfrac{2}{3}\)
\(b,\dfrac{6-2}{9-3}=\dfrac{4}{6}=\dfrac{2}{3}\Rightarrow\dfrac{6-2}{9-3}=\dfrac{2}{3}\)
\(\dfrac{2}{3}=\dfrac{6}{9}\Rightarrow\dfrac{6-2}{9-3}=\dfrac{6}{9}\)
\(2,a,\dfrac{3+12}{5+20}=\dfrac{15}{25}=\dfrac{3}{5}\Rightarrow\dfrac{3+12}{5+20}=\dfrac{3}{5}\)
\(\dfrac{3}{5}=\dfrac{3.4}{5.4}=\dfrac{12}{20}\Rightarrow\dfrac{3+12}{5+20}=\dfrac{12}{20}\)
\(b,\dfrac{3-12}{5-20}=\dfrac{-9}{-15}=\dfrac{9}{15}=\dfrac{3}{5}\Rightarrow\dfrac{3-12}{5-20}=\dfrac{3}{5}\)
\(\dfrac{3}{5}=\dfrac{3.4}{5.4}=\dfrac{12}{20}\Rightarrow\dfrac{3-12}{5-20}=\dfrac{12}{20}\)
2+39+3=512a,2+39+3=512
⇔512=5.312.3=1536⇔512=5.312.3=1536 và 69=243669=2436
1536<2436⇒512<691536<2436⇒512<69 hay 2+39+3<692+39+3<69
23=812⇒512<2323=812⇒512<23 hay 2+39+3<232+39+3<23
b,6−29−3=46=23⇒6−29−3=23b,6−29−3=46=23⇒6−29−3=23
23=69⇒6−29−3=6923=69⇒6−29−3=69
2,a,3+125+20=1525=35⇒3+125+20=352,a,3+125+20=1525=35⇒3+125+20=35
35=3.45.4=1220⇒3+125+20=122035=3.45.4=1220⇒3+125+20=1220
b,3−125−20=−9−15=915=35⇒3−125−20=35b,3−125−20=−9−15=915=35⇒3−125−20=35
35=3.45.4=1220⇒3−125−20=1220
