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Math Help - how do you find the intersection of

  1. #1
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    how do you find the intersection of

    so how do you find the intersection of

    x^2+y^2=18

    and

    y=x

    algebraically?
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  2. #2
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    Quote Originally Posted by behindDkeys View Post
    so how do you find the intersection of

    x^2+y^2=18

    and

    y=x

    algebraically?
    Substitute y=x into x^2+y^2=18

    Solve for x
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  3. #3
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    Quote Originally Posted by running-gag View Post
    Substitute y=x into x^2+y^2=18

    Solve for x

    but then i'll get like positive and negative 9

    do i substitute the value of x to each equation and right down what i got?

    then i'll get 4 solutions o.o

    is that right?
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  4. #4
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    No
    It leads to x=9
    Then x=-3 or x=3
    There are therefore 2 intersection points : (-3,-3) and (3,3)
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