College Algebra

Solve using Elimination or Substitution:

4x^2+9y^2=36
x+3y=3

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asked by Chris
  1. Ideal for substitution
    from the 2nd : x = 3 - 3y

    sub into 1st

    4(3-3y)^2 + 9y^2 = 36
    36 - 72y + 36y^2 + 9y^2 = 36
    45y^2 - 72y = 0
    5y^2 - 8y = 0
    y(5y-8) = 0
    y = 0 or y = 8/5

    if y = 0 , x = 3

    if y = 8/5 , then x = 3-24/5 = -9/5

    intersection points (3,0) and (-9/5, 8/5)

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    posted by Reiny
  2. Thanks for the help.

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    posted by Chris

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