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15 tháng 2 2016

\(\frac{42}{54}=\frac{7}{9}=\frac{7}{x}=\frac{21}{27}=\frac{y}{27}\Rightarrow x=9;y=21.\)

15 tháng 2 2016

bài toán @gmail.com

13 tháng 2 2020

\(\frac{7}{-9}=\frac{-21}{27}=\frac{-42}{54}\)

19 tháng 2 2021

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22 tháng 2 2021

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22 tháng 2 2021

a) \(\frac{x}{6}=\frac{5}{24}\Rightarrow x=\frac{5}{24}.6=\frac{5}{4}\)

b) \(-\frac{4}{y}=\frac{20}{14}\Rightarrow y=-4:\frac{20}{14}=-\frac{14}{5}\)

c) \(\frac{4}{7}=\frac{12}{x}\Rightarrow x=12:\frac{4}{7}=21\)

d) \(\frac{3}{7}=\frac{y}{21}\Rightarrow y=\frac{3}{7}.21=9\)

11 tháng 5 2016

\(\frac{5}{7}\).(\(\frac{1}{2}\)-\(\frac{1}{3}\)+\(\frac{4}{7}\)) +(\(\frac{1}{2}\)-\(\frac{1}{3}\)+\(\frac{4}{7}\)):\(\frac{7}{5}\)

\(\frac{5}{7}\).(\(\frac{1}{2}\)-\(\frac{1}{3}\)+\(\frac{4}{7}\))+(\(\frac{1}{2}\)-\(\frac{1}{3}\)+\(\frac{4}{7}\)).\(\frac{5}{7}\)

=2.\(\frac{5}{7}\).(\(\frac{1}{2}\)-\(\frac{1}{3}\)+\(\frac{4}{7}\))

=\(\frac{10}{7}\).(\(\frac{21}{42}\)-\(\frac{8}{42}\)+\(\frac{24}{42}\))

=\(\frac{10}{7}\).\(\frac{37}{42}\)=\(\frac{185}{147}\)

15 tháng 2 2019

7/x=y/27=-42/54=-7/9

7/x=-7/9 nên x=-9

y/27=-7/9=-21/27 nên y=-21

19 tháng 2 2021

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24 tháng 2 2019

a) Ta có: \(\frac{3+x}{5+y}=\frac{3}{5}\)

=> (3 + x).5 = 3(5 + y)

=> 15 + 5x = 15 + 3y

=> 5x = 3y

=> x = 3/5y

Mà x + y = 16

hay 3/5y + y = 16

=> (3/5 + 1).y = 16

=> 8/5.y = 16

=> y = 16 : 8/5

=> y = 10

=> x = 16 - 10 = 6

Vậy x = 6; y = 10

24 tháng 2 2019

b) Ta có: \(\frac{x-7}{y-6}=\frac{7}{6}\)

=> (x - 7).6 = 7.(y - 6)

=> 6x - 42 = 7y - 42

=> 6x = 7y

=> x = 7/6y

Mà x - y = -4

hay 7/6y - y = -4

=> 1/6y = -4

=> y = -4 : 1/6

=> y = -24

=> x = -4 - 24 = -28

Vậy x =  -28; y = -24

4 tháng 1 2016

45-|-27-(-25)-x|=-7+27

45-|-27-(-25)-x|=20

|-27-(-25)-x|=45-20

|-27-(-25)-x|=25

|-2-x|=25

=>-2-x=25 hoặc -2-x=-25

*Nếu -2-x=25 => x=-2-25=-27

*Nếu -2-x=-25 => x=(-2)-(-25)=23

Vậy x=-27 hoặc x=23

tick hộ mình nha