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Birthday polynomials!

March 29, 2008 pm31 10:37 pm

I posted last week about “birthday triangles” (in short, turn your birthdate of November 23, 1972 into a triangle with coordinates (1,1) (2,3) (7,2) – or a quadrilateral by including (1,9) – and then perform coordinate geometry or transformational geometry tasks using them.)

Sam, in the comments, suggested using birthdays to create polynomials. Cool. (How will this work?)

And then I remembered “family curves”

Express a birthday (yours, your mom’s, doesn’t matter who) as three coordinates: (1,1), (2,3), (7,2) – and write the equation of the parabola that passes through these three points. I used this as an early transition to polynomial functions last time I taught precalculus. It was also probably the only time the kiddies saw a system of 3 equations, 3 unkowns, before college

I’ll leave it to commenters to solve. Or solve your own. Or discuss which birthdays don’t make vertically oriented parabolas (parabolae?) or any parabola/s/e at all.

Edit – a friend points out that a (0,b) coordinate should either be required or somehow banned, as the work with and without the y-intercept given is of considerably different difficulty.

5 Comments leave one →
  1. March 31, 2008 am31 4:10 am 4:10 am

    My parabola would be a flatline (like you don’t want to see on the heart monitor) since it’s (0,8) (0,8) (7,8)

    How sad :(

  2. March 31, 2008 am31 5:24 am 5:24 am

    y=ax^2 +bx + c, but for you, you have all sorts of choices:

    y = kx(x-8) , choose whatever k you like. If you were August 18, a and b would need to be 0 – I’d call that a double-degenerate parabola (just to entertain the kiddies).

    And (7,8)? Way to make me feel old, dude!

  3. samjshah permalink
    March 31, 2008 am31 6:23 am 6:23 am

    so had exactly your idea at first, but i wanted to do something cool with the idea, but was thwarted and stymied (temporarily… i hope)


  4. jill lynn permalink
    October 1, 2009 am31 5:08 am 5:08 am

    can you give me the best or lucky day of giving birth in the month of november? i’m just thinking of the date between nov. 15 to 25.


  1. Birthday Polynomials « Continuous Everywhere but Differentiable Nowhere

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