Using the substitution method how would you solve the linear system?

2c-d= -2

4c+d=20

2 Answers

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  • 1 decade ago
    Favorite Answer

    Number your equations first, to keep track of them.

    1. 2c-d=-2

    2. 4c+d=20

    Solve one of them for d. I'll use the first:

    1. 2c-d=-2

    2c+2=d

    Put that into the second formula as d.

    2. 4c+d=20

    4c+(2c+2)=20

    Solve for c.

    6c+2=20

    6c=18

    c=3

    Once you've got c, all you have to do is put it back into one of the equations and find d.

    1. 2c-d=-2

    2(3)-d=-2

    6-d=-2

    6+2=d

    8=d

    These lines cross at the point (3,8)

  • John V
    Lv 6
    1 decade ago

    from 1, d = 2c +2

    so 4c + 2c + 2 = 20

    6c = 18

    c = 3

    2*3 - d = -2

    d = 8

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