Question

Срочно до завтра решите подробно

Answer 1

1) Общий знаменатель 12
    4х/12 + х/12 = 45/12
    4х + х = 45
    5х = 45
      х = 9
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2) 2 - 3(х +2) = 5 - 2х
    2 - 3х - 6 = 5 - 2х
    - 3х + 2х = 5 + 6 - 2
      - х = 9
        х = - 9
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3) 10х^2 + 5x = 0
     5x (2x + 1) = 0
     5x = 0
      x1 = 0
     2x + 1 = 0
     2x = - 1
    x2 = - 0,5
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4) 4 - 36x^2 = 0
    36x^2 = 4
    x^2 = 1/9
    x1 = 1/3
    x2 = - 1/3
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5) 2x^2 + 3x - 5 = 0
    D = 9 - 4*(-5)*2 = 9 + 40 = 49;    √D = 7
    x1 = (-3 + 7)/ 4 = 1
    x2 = (-3 - 7)/4 = - 2,5 
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6) 12 - x^2 = 11
     x^2 = 12 - 11
     x^2 = 1
     x1 = 1
     x2 = - 1
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7) (10x - 4)(3x + 2) = 0
    30x^2 - 12x + 20x - 8 = 0
    30x^2 + 8x - 8 = 0
    15x^2 + 4x - 4 = 0
     D = 16 - 4*(-4)*15 = 16 + 240 = 256;     √D = 16
     x1 = (-4 + 16)/30 = 12/30 = 6/15
     x2 = (- 4 - 16)/30 = - 2/3
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8) 7(x-3) = 2(x + 1)
    7x - 21 = 2x + 2
    7x - 2x = 21 + 2
    5x = 23
      x = 4,6