Question:

Substitution math?

by  |  earlier

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hey guys im stuck

what would i do

y=4x-1

y=2x-5

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2 ANSWERS


  1. 2x-5=4x-1

    x= -2, y=-9


  2. What he said is a perfectly legitimate way of doing it.

    Another way is to solve the first for x:

    y = 4x - 1

    y + 1 = 4x

    (y + 1) / 4 = x

    Then plug that into the second:

    y = (y + 1) / 2 - 5

    y + 5 = (y + 1) / 2

    2y + 10 = y + 1

    y = - 9

    Now that we know y we use it to solve x:

    y = 4x - 1 (the thing you started out with, put -9 in for y)

    -9 = 4x - 1

    -8 = 4x

    -2 = x
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