Math

Solve using substitution
3x - 9y = 3
6x - 3y = -24

Solve using elimination
y - 1/2x = 6
2x + 6y = 19

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asked by Josh
  1. 3x - 9y = 3
    6x - 3y = -24

    from the first, divide by 3
    x - 3y = 1
    x = 3y+1

    sub into the 2nd
    6(3y+1) - 3y = -24
    18y + 6 - 3y = -24
    15y = -30
    y = -2
    then x = -6+1 = -5

    for the 2nd system, multiply the 1st by -4
    2x -4y = -24
    2x + 6y = 19
    subtract them
    10y = 43
    y = 43/10 = 4.3
    into the 2nd:
    2x + 6(4.3) = 19
    2x = 19 - 25.8
    2x = -6.8
    x = -3.4

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    posted by Reiny
  2. Eq1: 3x - 9y = 3
    Eq2: 6x - 3y = -24

    In Eq1, solve for X:
    3x = 9y + 3
    X = 3y+1

    In Eq2, replace X with 3y+1:
    6(3y+1) - 3y = -24
    18y+6 - 3y = -24
    15y = -30
    Y = -2.

    In Eq1, replace Y with-2:
    3x-9*(-2) = 3
    3x + 18 = 3
    3x = -15
    X = -5.

    Solution set: (-5,-2).

    Eq1: Y - X/2 = 6
    Eq2: 2x + 6y = 19

    Multiply Eq1 by 4 and add Eq2:
    -2x + 4y = 24
    +2x + 6y = 19
    Sum: 10y = 43
    Y = 4.3

    In Eq1, replace Y with 4.3:

    4.3 - 0.5x = 6
    -0.5x = 1.7
    X = -3.4

    Solution set: (-3.4,4.3).

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    posted by Henry
  3. Reiny, we meet again!! LOL! Oh well, we
    got the same answer!

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    posted by Henry

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