Mathematics

Question

solve the linear system using substitution.
4x - y =5
4x + 4y = -4

1 Answer

  • 4x - y =5 
    4x + 4y = -4

    Change all the signs of the first equation
    -4x + y = -5
    Add 4x to both sides
    y == 4x - 5

    Substitute for y in second equation

    4x + 4(4x - 5) = -4

    4x + 16x - 20 = -4

    20x - 20 = -4

    Add 20 to both sides

    20x = 16

    Divide both sides by 20

    x = 16/20 === 4/5

    Substitute to find y

    y == 4x - 5 == 4(4/5) - 5 == 16/5  - 5 =  -9/5

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