algebra

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Solving Systems by Substitution:

2. x=1-4y
2x+7y=3

I need help learning how to do this problem step-by-step

  • algebra -

    your first equation says that
    x = 1-4y

    so "substitute" 1-4y wherever you see x in the other equation

    2x+7y=3
    2(1-4y) + 7y = 3
    2 - 8y + 7y = 3
    -y = 1
    y = -1

    next sub that y = -1 back into the first equation
    x = 1 - 4(-1) = 1+4 = 5

  • algebra -

    x = 1-4y
    2x+7y=3

    Starting with the first equation
    since x = 1 - 4y

    Plug that in to the second equation

    2(1-4y)+7y=3
    2 -8y + 7y = 3
    2 - y = 3
    2/2 - y = 3/2
    - y = 3/2

    Since why can't be negative, move the negative over to the other side

    y = -3/2
    Okay we found what Y is now plug that into the first equation

    x = 1-4(-3/2)
    x = 1 + 6
    x = 7

    so the answer is (7,-3/2)

    I'm pretty sure this is right, but I hope a real tutor comes and say for sure

  • algebra -

    Oh sorry, I did my math wrong and Divided instead of subtracting.

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