Hin Pand asked in 科學及數學數學 · 1 decade ago

二元一次方程

1. 3X+7Y÷2=12

5Y-2X÷3=32

2. X÷3+Y÷2=2

Y÷6-X÷4=- 8

請例式

3 Answers

Rating
  • 1 decade ago
    Best Answer

    3X+7Y÷2=12-----1

    5Y-2X÷3=32-----2

    6x+7y=24---3

    15y-2x=96---4

    x=(24-7y)/6

    putx=(24-7y)/6 into 4

    15y-2(24-7y)/6=96

    45y-24+7y=288

    y=6

    x=(24-42)/6

    x=-3

    X÷3+Y÷2=2--1

    Y÷6-X÷4=- 8---2

    2x+3y=12---3

    2y-3x=-96---4

    x=(12-3y)/2

    2y-3(12-3y)/2=-96

    4y-36+9y=-192

    y=-12

    x=(12-3y)/2

    x=24

  • 1 decade ago

    1. 3X+7Y÷2=12... (1)

    5Y-2X÷3=32... (2)

    (1)x2: 6X + 7Y = 24... (3)

    (2)x9: 45Y - 6X = 288.. (4)

    (3) + (4):

    6X + 7Y + 45Y - 6X = 24 + 288

    52Y= 312

    Y= 6 (ans)

    以Y=6代入(3):

    6X + 7x6 = 24

    6X= 24 - 42 = 18

    X = 3 (ans)

    2. X/3 + Y/2 = 2... (1)

    Y/6 - X/4 = 8... (2)

    (1)x18: 6X + 9Y = 36 ... (3)

    (2)x12: 4Y - 6X = -192.. (4)

    (3) + (4):

    6X + 9Y + 4Y - 6X = 36 - 192

    13Y = - 156

    Y = -12 (ans)

    以Y=-12代入(4):

    -12x4 - 6X = -192

    - 6X = -192 + 48 = -144

    X = 24 (ans)

  • Anonymous
    1 decade ago

    1. 3X+7Y÷2=12 . . . . (1)

    5Y-2X÷3=32 . . . . . . (2)

    (1) x 2 : 6X+7Y=24 . . . . . (3)

    (2) x 3 : 15Y-2X=96

    45Y-6X=288 . . . . . . . . . . . . (4)

    (3)+(4) : 52Y=312

    Y=6

    代入(1) : 3X+21=12

    X=-3

    2. X÷3+Y÷2=2 . . . . . (1)

    Y÷6-X÷4=- 8 . . . . . . (2)

    (1) x 6 : 2X+3Y=12 . . . . . (3)

    (2) x 12 : 2Y-3X=- 96 . . . (4)

    (3) x 2 : 4X+6Y=24 . . . . . . . . . (5)

    (4) x 3 : 6Y-9X=- 288 . . . . . . . . (6)

    (5)-(6): 13X=312

    X=24

    Y=-12

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