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anonymous

  • 4 years ago

Find the equation of the quadratic that has x-intercepts f(2)=0 and f(-6)=0 in vertex form.

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  1. amistre64
    • 4 years ago
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    vertex x is half way between intercepts

  2. amistre64
    • 4 years ago
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    so its at least got vertex on the x=-2 axis

  3. anonymous
    • 4 years ago
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    how would i set it up then

  4. amistre64
    • 4 years ago
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    2+-6 = -4/2 = -2

  5. anonymous
    • 4 years ago
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    then how would I find the y

  6. amistre64
    • 4 years ago
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    f(x) = a(x+2)^2 + h

  7. amistre64
    • 4 years ago
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    err, i think its +k for standard usage

  8. anonymous
    • 4 years ago
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    yeah but how would i figure out k and the slope?

  9. amistre64
    • 4 years ago
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    without any other information; your pretty much at a stand still; there is a whole family of equations to fit this

  10. amistre64
    • 4 years ago
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    if k is negative; make a + and f(x) = a(x+2)^2 - k or the other way around since the vertex needs to be on the oterside of the opening end f(x) -a(x+2)^2 + k

  11. amistre64
    • 4 years ago
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    |dw:1327365880607:dw|

  12. amistre64
    • 4 years ago
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    anything but zeros for k and a should work, and make sure they gots opposite signs

  13. anonymous
    • 4 years ago
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    one sec let me test it

  14. anonymous
    • 4 years ago
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    but whats the slope then?

  15. amistre64
    • 4 years ago
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    hmmm, i just tested a few on the wolf, my thoughts need some refinement :)

  16. amistre64
    • 4 years ago
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    ok, try this; make k equal to half the distance between intercepts; in this case -4 should work for i trial run

  17. amistre64
    • 4 years ago
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    .... recalculating lol we are sitting at 4; so if x=4 x^2 = 16 .... lets try -16 hope this aint to confusing yet

  18. amistre64
    • 4 years ago
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    http://www.wolframalpha.com/input/?i=y%3D%28x%2B2%29%5E2+-+16

  19. amistre64
    • 4 years ago
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    that one hit, i knew one of my ideas had to stick ;)

  20. anonymous
    • 4 years ago
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    so the slope is 1?

  21. amistre64
    • 4 years ago
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    |dw:1327366276767:dw|

  22. amistre64
    • 4 years ago
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    yes

  23. anonymous
    • 4 years ago
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    thanks!

  24. amistre64
    • 4 years ago
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    a simpler way would have been to construct an equation form the zeros: a(x+6)(x-2)=0 but it wouldnt have been in vertex form

  25. anonymous
    • 4 years ago
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    Thats ok, at least we found it :)

  26. amistre64
    • 4 years ago
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    :) good luck

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