У выражение: 7(Х—3) –4(Х – 5)

3x-1

Пошаговое объяснение:

7(x-3)-4(x-5)

7x-21+4x-20

3x-21+20

3x-1

ответ: 3x-1

Пошаговое объяснение:

7(x-3)-4(x-5)

7x-21+4x-20

3x-21+20

3x-1

C – 73

 a) x = -2

 б) x = -9.5

  в)  x = 7.77

C – 74

 a) x = -1

 б) x = 0.8

  в)  x = 0.83

C – 75

 a) x = 26

  б) x = 0.5

  в) x = 7

Пошаговое объяснение:

C – 73

 a) -2x = 16 = 5x + 30

       -2x – 5x = 30 – 16

       -7x = 14

       x = 14 : -7

        x = -2

б)  3 1/4 x – 4 5/7 = 3 5/12 x  – 3 3/14  

     3 1/4x – 3 5/12x = 4 5/7 – 3 3/14

     3 3/12x – 3 5/12 x = 4 10/14 – 3 3/14

     -2/12x = 1 7/12

     -2/12x = 19/12

      x = (19/12)/ (-2/12)

     x = -9.5

в) 5/12 – 7/9 x = 10 5/12 – 3x

   -7/9x + 3x = 10 5/12 – 5/12

   2.22 x = 10

  x = 7.77

C – 74

a) 4(1 - 0.5x) = -2( 3 + 2x)

       4 – 2x = -6 – 4x

       -2x + 4x = -6 + 4

       2x = -2

       x = -2/2

       x = -1

б)    5(x + 1.2) = 12.5x

        5x + 6 = 12.5x

        12.5x – 5x = 6

       7.5x =6

        x = 6/ 7.5

       x = 0.8

   в)  1/2(4 – 3 1/2 x) = 1 1/4x – 1/2

        2 – 1.75x = 1.25x – 0.5

       1.25x + 1.75x = 2 + 0.5

       3x = 2.5

       x = 2.5/ 3

       x = 0.83

c – 75

a) -3(2.1x – 4) – 4.2 = 1.2(-5x + 0.5)

     -6.3x + 12.6 – 4.2 = -6x + 0.6

      -6x + 6.3x = 8.4 – 0.6

      0.3x = 7.8

      x = 7.8/ 0.3

      x = 26

б) 6.4(2-3x) = 6(0.8x – 1) + 6.8

   12.8 – 19.2x = 4.8x – 6 + 6.8

   4.8x + 19.2x  =  12.8 – 0.8

   24x = 12

    x = 12/ 24  

    x = 0.5

в) (5.8x – 40.1)/0.8 = ( 3.2x – 23.9)/-2.4

   -3(5.8x – 40.1)/-2.4 = (3.2x – 23.9)/-2.4

   -17.4x + 120.3 = 3.2x – 23.9

   3.2x + 17.4x = 120.3 + 23.9

   20.6 x = 144.2

    x = 144.2/ 20/6

    x = 7