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12 September, 01:44

9a-2b=-8 - 7a+3b=12 system of equations by elimination

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Answers (2)
  1. 12 September, 01:49
    0
    9a - 2b = - 8

    -7a + 3b = 12

    Multiply the first equation by 3:

    9a - 2b = - 8

    27a - 6b = - 24

    Multiply the 2nd equation by 2:

    -7a + 3b = 12

    -14a + 6b = 24

    Add the two equations:

    27a - 6b = - 24

    -14a + 6b = 24

    13a + 0 = 0

    13a = 0

    Divide 13 to both sides:

    a = 0

    Plug this into any of the two equations to find 'b':

    9a - 2b = - 8

    9 (0) - 2b = - 8

    -2b = - 8

    Divide - 2 to both sides:

    b = 4

    So the solution is (0, 4).
  2. 12 September, 01:59
    0
    So,

    9a - 2b = - 8

    -7a + 3b = 12

    Elimination by Addition

    Multiply both sides of the first equation by 3

    27a - 6b = - 24

    Multiply both sides of the second equation by 2

    -14a + 6b = 24

    Add the two equations together

    13a = 0

    Divide both sides by 13

    a = 0

    Substitute 0 for a in the first equation

    9 (0) - 2b = - 8

    0 - 2b = - 8

    -2b = - 8

    Divide both sides by - 2

    b = 4

    Check

    9 (0) - 2 (4) = - 8

    0 - 8 = - 8

    -8 = - 8 This checks.

    -7 (0) + 3 (4) = 12

    0 + 12 = 12

    12 = 12 This also checks.

    S = { (0,4) }
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