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a: 20/30=2/3
30/45=2/3
=>20/30=30/45
b: -25/35=-5/7
-55/77=-5/7
=>-25/35=-55/77
\(a,\dfrac{20}{30}=\dfrac{30}{45}v\text{ì}20.45=30.30=900\\ b,\dfrac{-25}{35}=\dfrac{-55}{77}v\text{ì}:\left(-25\right).77=35.\left(-55\right)=-1925\)
a) Ta có:
\(\dfrac{36}{84}=\dfrac{3}{7}\) ; \(\dfrac{42}{98}=\dfrac{3}{7}\)
\(\Rightarrow\dfrac{36}{84}=\dfrac{42}{98}\left(=\dfrac{3}{7}\right)\)
b) Ta có :
\(\dfrac{123}{237}=\dfrac{41}{79}\) ; \(\dfrac{123123}{237237}=\dfrac{41}{79}\)
\(\Rightarrow\dfrac{123}{237}=\dfrac{123123}{237237}\)
a) Ta rút gọn phân số:
\(\dfrac{36}{84}\)=\(\dfrac{36:12}{84:12}\)=\(\dfrac{3}{7}\)
\(\dfrac{42}{98}\)=\(\dfrac{42:14}{98:14}\)=\(\dfrac{3}{7}\)
Vì \(\dfrac{3}{7}\)=\(\dfrac{3}{7}\) nên \(\dfrac{36}{84}\)=\(\dfrac{42}{98}\)
\(\dfrac{20}{30}=\dfrac{20:10}{30:10}=\dfrac{2}{3}\)
\(\dfrac{30}{45}=\dfrac{30:15}{45:15}=\dfrac{2}{3}\)
Ta thấy\(\dfrac{2}{3}=\dfrac{2}{3}\Rightarrow\dfrac{20}{30}=\dfrac{30}{45}\)
Bài 2:
a: -2*(-27)=54
6*9=54
=>Hai phân số này bằng nhau
b: -1/-5=1/5=5/25<>4/25
Bài 3:
a: =>16/x=-4/5
=>x=-20
b: =>(x+7)/15=-2/3
=>x+7=-10
=>x=-17
a: \(\dfrac{20}{30}=\dfrac{2}{3}\)
\(\dfrac{30}{45}=\dfrac{2}{3}\)
Do đó: \(\dfrac{20}{30}=\dfrac{30}{45}\)
b: \(\dfrac{-25}{35}=\dfrac{-5}{7}\)
\(\dfrac{-55}{77}=\dfrac{-5}{7}\)
Do đó: \(-\dfrac{25}{35}=-\dfrac{55}{77}\)
a,20/30=2/3
30/45=2/3
->20/30=30/45
b -25/35=-5/7
-55/77=-5/7
-> -25/35=-55/77