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a) \(12.20=15.16\)
\(\Rightarrow\frac{12}{15}=\frac{16}{20};\frac{15}{12}=\frac{20}{16};\frac{20}{15}=\frac{16}{12};\frac{12}{16}=\frac{15}{20}\)
b) \(2,4.3,2=8.0,96\)
\(\Rightarrow\frac{2,4}{8}=\frac{0,96}{3,2};\frac{8}{2,4}=\frac{3,2}{0,96};\frac{3,2}{8}=\frac{0,96}{2,4};\frac{2,4}{0,96}=\frac{8}{3,2}\)
\(1.\)
\(a,\)
\(7.\left(-28\right)=\left(-49\right).4\)
Ta có : \(\frac{7}{-49}=\frac{4}{-28}\) \(\frac{-28}{4}=\frac{-49}{7}\)
\(\frac{7}{4}=\frac{-49}{-28}\) \(\frac{-28}{-49}=\frac{4}{7}\)
\(b,\)
\(0,36.4,25=0,9.1,7\)
Ta có : \(\frac{0,36}{0,9}=\frac{1,7}{4,25}\) \(\frac{0,36}{1,7}=\frac{0,9}{4,25}\)
\(\frac{4,25}{0,9}=\frac{1,7}{0,36}\) \(\frac{4,25}{1,7}=\frac{0,9}{0,36}\)
a, vì 1.16 = 2.8
Vậy ta có các tỉ lệ thức: \(\dfrac{1}{2}\) = \(\dfrac{8}{16}\); \(\dfrac{1}{8}\) = \(\dfrac{2}{16}\); \(\dfrac{2}{1}\) = \(\dfrac{16}{8}\); \(\dfrac{16}{2}\) = \(\dfrac{8}{1}\)
b, \(\dfrac{3}{2}\) : \(\dfrac{2}{3}\) = \(\dfrac{1}{4}\) : \(\dfrac{1}{9}\) ⇒ \(\dfrac{3}{2}\).\(\dfrac{1}{9}\) = \(\dfrac{1}{4}\).\(\dfrac{2}{3}\)
\(\dfrac{3}{2}\) : \(\dfrac{1}{4}\) = \(\dfrac{2}{3}\) : \(\dfrac{1}{9}\)
\(\dfrac{1}{9}\) : \(\dfrac{1}{4}\) = \(\dfrac{2}{3}\) : \(\dfrac{3}{2}\)
\(\dfrac{1}{9}\) : \(\dfrac{2}{3}\) = \(\dfrac{1}{4}\) : \(\dfrac{3}{2}\)
Tỉ lệ thức là đẳng thức của hai tỉ số \(\frac{a}{b}=\frac{c}{d}\)
a) \(12.20=15.16\)
\(\Leftrightarrow\)\(\frac{12}{15}=\frac{16}{20}\) ; \(\frac{20}{15}=\frac{16}{12}\);
\(\Leftrightarrow\) \(\frac{12}{16}=\frac{15}{20}\); \(\frac{10}{16}=\frac{15}{12}\)
b) \(\left(a-b\right).\left(a+b\right)=2.3\)
\(\Leftrightarrow\)\(\frac{\left(a-b\right)}{2}=\frac{3}{\left(a+b\right)}\); \(\frac{\left(a-b\right)}{3}=\frac{2}{\left(a+b\right)}\)
\(\Leftrightarrow\)\(\frac{\left(a+b\right)}{3}=\frac{2}{\left(a+b\right)}\); \(\frac{\left(a+b\right)}{2}=\frac{3}{\left(a-b\right)}\)