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Cách 1:
\(\left(\dfrac{1}{3}+\dfrac{2}{9}\right)\times\dfrac{4}{9}\)
\(=\dfrac{5}{9}\times\dfrac{4}{9}\)
\(=\dfrac{20}{81}\)
Cách 2:
\(\left(\dfrac{1}{3}+\dfrac{2}{9}\right)\times\dfrac{4}{9}\)
\(=\dfrac{1}{3}\times\dfrac{4}{9}+\dfrac{2}{9}\times\dfrac{4}{9}\)
\(=\dfrac{4}{27}+\dfrac{8}{81}\)
\(=\dfrac{20}{81}\)
C1: \(\left(\dfrac{1}{3}+\dfrac{2}{9}\right)\)x\(\dfrac{4}{9}\)=\(\left(\dfrac{3}{9}+\dfrac{2}{9}\right)\text{x}\dfrac{4}{9}\)=\(\dfrac{5}{9}\text{x}\dfrac{4}{9}=\dfrac{20}{81}\)
C2: \(\left(\dfrac{1}{3}+\dfrac{2}{9}\right)\)x\(\dfrac{4}{9}\)=\(\dfrac{1}{3}\text{ x}\dfrac{4}{9}+\dfrac{2}{9}\text{ x}\dfrac{4}{9}\)=\(\dfrac{4}{27}+\dfrac{8}{81}=\dfrac{12}{81}+\dfrac{8}{81}=\dfrac{20}{81}\)
\(\frac{5}{7}+y\times\frac{1}{2}=\frac{8}{7}:\frac{3}{2}\)
=> \(\frac{5}{7}+y\times\frac{1}{2}=\frac{8}{7}\times\frac{2}{3}\)
=> \(\frac{5}{7}+y\times\frac{1}{2}=\frac{16}{21}\)
=> \(y\times\frac{1}{2}=\frac{16}{21}-\frac{5}{7}=\frac{1}{21}\)
=> \(y=\frac{1}{21}:\frac{1}{2}=\frac{1}{21}\cdot2=\frac{2}{21}\)
5/7 + Y x 1/2 = 8/7 : 3/2
=> 5/7 + Y x 1/2 = 16/21
=> Y x 1/2 = 16/21 - 5/7
=> Y x 1/2 = 1/21
=> Y = 1/21 : 1/2
=> Y = 2/21
Hok tốt ^^
a) y : 0,25 + y x 8 - y : 0,5 = 230
y x 4 + y x 8 - y x 2 = 230
y x (4 + 8 - 2) = 230
y x 10 = 230
y = 230 : 10
y = 23
b) \(x\) x 4 + \(x\) x 6 = 30
\(x\) x (4 + 6) = 30
\(x\) x 10 = 30
\(x\) = 30 : 10
\(x\) = 3
a; y :0,25 + y x 8 - y: 0,5 = 230
y x 4 + y x 8 - y x 2 = 230
y x (4 + 8 - 2) = 230
y x 10 = 230
y = 230 : 10
y = 23
b; \(x\) \(\times\) 4 + \(x\) \(\times\) 6 = 30
\(x\) \(\times\) (4 + 6) = 30
\(x\) \(\times\) 10 = 30
\(x\) = 30 : 10
\(x\) = 3
\(\frac{2}{5}\times\frac{1}{6}:2=\frac{2}{5}\times\frac{1}{6}\times\frac{1}{2}\)
\(=\frac{2}{5\times6\times2}\)(vì nhân với 1 không có giá trị nên mình lược bỏ
\(=\frac{1}{30}\)
@muối