Question

Tìm số hữu tỉ $x$, thoả mãn:

a) $ \dfrac{1}{5}+\dfrac{4}{5}: x=0,75$;

b) $x+\dfrac{1}{2}=1-x$.

Answer 1

\(a,1\dfrac{1}{5}+\dfrac{4}{5}:x=0,75\\ \dfrac{ 4}{5}:x=\dfrac{3}{4}-\dfrac{6}{4}\\ \dfrac{4}{5}:x=-\dfrac{3}{4}\\ x=\dfrac{4}{5}:\left(-\dfrac{3}{4}\right)\\ x=-\dfrac{16}{15}\\ b,x+\dfrac{1}{2}=1-x\\ x+x=1-\dfrac{1}{2}\\ 2x=\dfrac{1}{2}\\ x=\dfrac{1}{2}:2\\ x=\dfrac{1}{4}\)

Answer 2

15+45:x=0,7515+45:x=0,75

15+45:x=3415+45:x=34

45:x=34−1545:x=34−15

45:x=112045:x=1120

x=1611x=1611;

x+12=1−xx+12=1−x

2x=1−122x=1−12

2x=122x=12

x=14x=14.

Answer 3

15+45:x=0,7515+45:x=0,75

15+45:x=3415+45:x=34

45:x=34−1545:x=34−15

45:x=112045:x=1120

x=1611x=1611;

x+12=1−xx+12=1−x

2x=1−122x=1−12

2x=122x=12

x=14x=14.

 

Answer 4

$ \dfrac{1}{5}+\dfrac{4}{5}: x=0,75$;

b) $x+\dfrac{1}{2}=1-x$.

Em bị trục trặc và nhìn thấy phần câu hỏi bị thế này ạ. Em nhìn em không giải được ạ

Answer 5

a) $ \dfrac{1}{5}+\dfrac{4}{5}: x=0,75$

$ \dfrac{1}{5}+\dfrac{4}{5}: x=\dfrac{3}{4}$

$\dfrac{4}{5}: x=\dfrac{3}{4}-\dfrac{1}{5}$

$\dfrac{4}{5}: x=\dfrac{11}{20}$

$x=\dfrac{16}{11}$;

b) $x+\dfrac{1}{2}=1-x$

 $2x=1-\dfrac{1}{2}$

 $2x=\dfrac{1}{2}$

 $x=\dfrac{1}{4}$.

Answer 6

.

Answer 7

a) \(x=\dfrac{16}{11}\)
b) \(x=\dfrac{1}{4}\)

Answer 8

a,151​+54​:x=0,7554​:x=43​−46​54​:x=−43​x=54​:(−43​)x=−1516​b,x+21​=1−xx+x=1−21​2x=21​x=21​:2x=41​

Answer 9

b) x+\dfrac{1}{2}=1-xx+21​=1−x

 2x=1-\dfrac{1}{2}2x=1−21​

 2x=\dfrac{1}{2}2x=21​

 x=\dfrac{1}{4}x=41​.

Answer 10

a, 1/5 + 4/5 : x = 3/4

4/5 : x = 3/4 - 1/5

4/5 : x = 11/20.

 

b, 2x = 1 - 1/2.

2x = 1/2

x = 1/4

Answer 11

a)\(\dfrac{1}{5}+\dfrac{4}{5}:x=0,75\)

=>\(\dfrac{1}{5}+\dfrac{4}{5}:x=\dfrac{3}{4}\)

=>        \(\dfrac{4}{5}:x=\dfrac{3}{4}-\dfrac{1}{5}\)

=>        \(\dfrac{4}{5}:x=\dfrac{15}{20}-\dfrac{4}{20}\)

=>        \(\dfrac{4}{5}:x=\dfrac{11}{20}\)

=>              \(x=\dfrac{4}{5}:\dfrac{11}{20}\)

=>              \(x=\dfrac{4}{5}.\dfrac{20}{11}\)

=>              \(x=\dfrac{16}{11}\)

Vậy \(x=\dfrac{16}{11}\)

b)\(x+\dfrac{1}{2}=1-x\)

=>\(x+x=1-\dfrac{1}{2}\)

=>\(2x=\dfrac{1}{2}\)

=>\(x=\dfrac{1}{2}:2\)

=>\(x=\dfrac{1}{2}.\dfrac{1}{2}\)

=>\(x=\dfrac{1}{4}\)

Vậy \(x=\dfrac{1}{4}\)

Answer 12

a, 1/5 + 4/5 : x = 0,75 => 1/5 + 4/5 : x = 3/4 => 4/5 : x = 3/4 - 1/5 => 4/5 : x = 11/20 => x = 4/5 : 11/20 = 11/16 . Vậy x = 11/16

b, x + 1/2 = 1 - x => x + x = 1 - 1/2 => 2x = 1/2 => x = 1/2 : 2 => x = 1/4 . Vậy x = 1/4

Answer 13

a)  \dfrac{1}{5}+\dfrac{4}{5}: x=0,75 51​+54​:x=0,75

 \dfrac{1}{5}+\dfrac{4}{5}: x=\dfrac{3}{4} 51​+54​:x=43​

\dfrac{4}{5}: x=\dfrac{3}{4}-\dfrac{1}{5}54​:x=43​−51​

\dfrac{4}{5}: x=\dfrac{11}{20}54​:x=2011​

x=\dfrac{16}{11}x=1116​;

b) x+\dfrac{1}{2}=1-xx+21​=1−x

 2x=1-\dfrac{1}{2}2x=1−21​

 2x=\dfrac{1}{2}2x=21​

 x=\dfrac{1}{4}x=41​

Answer 14

a, \(\dfrac{1}{5}\)+\(\dfrac{4}{5}\):x=0,75

\(\dfrac{1}{5}\) + \(\dfrac{4}{5}\) : x =\(\dfrac{3}{4}\)

         \(\dfrac{4}{5}\): x = \(\dfrac{3}{4}\) - \(\dfrac{1}{5}\)

         \(\dfrac{4}{5}\): x = \(\dfrac{11}{20}\)

              x = \(\dfrac{4}{5}\) : \(\dfrac{11}{20}\)

              x = \(\dfrac{16}{11}\)

b,x + \(\dfrac{1}{2}\)= 1 - x 

2x = 1 - \(\dfrac{1}{2}\)

2x = \(\dfrac{1}{2}\)

  x = \(\dfrac{1}{4}\)

Answer 15

a,1/5+4/5:x=0,75                                                 b, x+1/2= 1-x

    1/5+4/5:x= 3/4                                                    x+1/2+x= 1

           4/5:x= 3/4-1/5                                              2x+1/2  = 1

           4/5:x= 11/20                                                 2x         = 1-1/2

                 x= 4/5:11/20                                           2x         = 1/2

                 x= 16/11                                                   x         = 1/2:2

Vậy x= 16/11                                                             x         = 1/4

                                                                       Vậy x=1/4

Answer 16

a)1/5+4/5:X=0,75       b)x+1/2=1-x

=>1/5+4/5.1/x=3/4    =>x+x=1-1/2

=>1/5+4/5x=3/4        =>2x=1/2

=>4/5x=3/4-1/5        =>x=1/4

=>4/5x=11/20

=>x=16/11

Answer 17

a)  \dfrac{1}{5}+\dfrac{4}{5}: x=0,75 51​+54​:x=0,75

 \dfrac{1}{5}+\dfrac{4}{5}: x=\dfrac{3}{4} 51​+54​:x=43​

\dfrac{4}{5}: x=\dfrac{3}{4}-\dfrac{1}{5}54​:x=43​−51​

\dfrac{4}{5}: x=\dfrac{11}{20}54​:x=2011​

x=\dfrac{16}{11}x=1116​;

b) x+\dfrac{1}{2}=1-xx+21​=1−x

 2x=1-\dfrac{1}{2}2x=1−21​

 2x=\dfrac{1}{2}2x=21​

 x=\dfrac{1}{4}x=41​.

Answer 18

a)3/20 

b) 0,25

Answer 19

a) 19/16

b) 1

Answer 20

khong viet duoc phan so

Answer 21

a)\(\dfrac{1}{5}+\dfrac{4}{5}:x=0 \)

\(1:x=0\)

\(x=1:0\)

\(x=0\)

b)\(x+\dfrac{1}{2}=1-x\)

\(x=\dfrac{1}{4}\)

Answer 22

\(a,\dfrac{1}{5}+\dfrac{4}{5}:x=0,75\)

\(\dfrac{1}{5}+\dfrac{4}{5}:x=\dfrac{3}{4}\)

\(\dfrac{4}{5}:x=\dfrac{3}{4}-\dfrac{1}{5}\)

\(\dfrac{4}{5}:x=\dfrac{11}{20}\)

\(x=\dfrac{16}{11}\)

b,\(x+\dfrac{1}{2}=1-x\)

\(2x=1-\dfrac{1}{2}\)

\(2x=\dfrac{1}{2}\)

\(x=\dfrac{1}{4}\)

 

Answer 23

    

Answer 24

a)1/5 + 4/5 : x = 0.75

          1      : x = 3/4

                     x = 3/4 . 1

                      x = 3/4

 

Answer 25

a, 1/5 + 4/5 : x = 0,75   1:x=0,75  x= 0,75 .1 = 0,75             b,x+1/2= 1-x      x= 1/2 -1=-1/2

Answer 26

Answer 27

a) 1/5 + 4/5 : x = 0,75

1/5 + 4/5 : x = 3/4

4/5 : x = 3/4 - 1/5

4/5 : x = 11/20

x = 4/5 : 11/20

x = 16/11

Vậy x = 16/11

b) x + 1/2 = 1 - x

( x . 2 ) + 1/2 = 1

( x . 2 ) = 1 - 1/2

x . 2 = 1/2

x = 1/2 : 2

x = 1/4

Vậy x = 1/4

 

Answer 28

    

 

Answer 29

Answer 30

a)\(\dfrac{1}{5}+\dfrac{4}{5}:x=0,75\)

           \(\dfrac{4}{5}:x=\dfrac{3}{4}-\dfrac{1}{5}\)

           \(\dfrac{4}{5}:x=\dfrac{11}{20}\)

                 \(x=\dfrac{4}{5}:\dfrac{11}{20}=\dfrac{4}{5}.\dfrac{20}{11}=\dfrac{16}{11}\)

b)\(x+\dfrac{1}{2}=1-x\)

   \(x+x=1-\dfrac{1}{2}\)

        \(2x=\dfrac{1}{2}\)

          \(x=\dfrac{1}{2}:2=\dfrac{1}{4}\)