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tbrooks3 Group Title

Find the minimum value for the function: y = x^2 + 9x + 18

  • 2 years ago
  • 2 years ago

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  1. samjordon Group Title
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    do u knwo how to complete the square? or do u factor it?

    • 2 years ago
  2. samjordon Group Title
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    lets factor its easy

    • 2 years ago
  3. tbrooks3 Group Title
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    its under my quadratic function lesson so idk

    • 2 years ago
  4. samjordon Group Title
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    what 2 numbers when you multiply them =18 and when u add them =9?

    • 2 years ago
  5. tbrooks3 Group Title
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    is there a number for that?

    • 2 years ago
  6. samjordon Group Title
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    6*3=18 6+3=9

    • 2 years ago
  7. tbrooks3 Group Title
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    ohhh

    • 2 years ago
  8. tbrooks3 Group Title
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    so is the answer 9 ?

    • 2 years ago
  9. samjordon Group Title
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    yaaaa factoring i just taught this to my class today. hmmmm nooooo we r factoring. We r trying to figure out 2 numbers that when u mulyiply them give us 18 and when u add them gives us 9

    • 2 years ago
  10. satellite73 Group Title
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    finding the zeros is a long and complicated way to find the minimum

    • 2 years ago
  11. samjordon Group Title
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    umm well we can complete the square

    • 2 years ago
  12. samjordon Group Title
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    but i dont think she knows that

    • 2 years ago
  13. Zarkon Group Title
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    use the vertex formula

    • 2 years ago
  14. satellite73 Group Title
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    minimum is at the vertex, and first coordinate of the vertex of \[y=ax^2+bx+c\] is always \(-\frac{b}{2a}\)

    • 2 years ago
  15. tbrooks3 Group Title
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    when doing the vertx thing... is the second number the minimum?

    • 2 years ago
  16. satellite73 Group Title
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    in your case it is \(-\frac{9}{2}\) replace \(x\) by \(-\frac{9}{2}\) to find the minimum

    • 2 years ago
  17. satellite73 Group Title
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    minimum means minimum value of \(y\) so it is the second coordinate, not the first

    • 2 years ago
  18. satellite73 Group Title
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    so yes, what you said, the second number is the minimum.

    • 2 years ago
  19. samjordon Group Title
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    ohhh i like this method. We never learnt this stuff. Like the textbook always made us complete the square. oh cooll

    • 2 years ago
  20. tbrooks3 Group Title
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    can i just plug it into my graphing calculator to get the anwser ?

    • 2 years ago
  21. satellite73 Group Title
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    completing the square is for suckers, unless of course you are solving a quadratic equation

    • 2 years ago
  22. lgbasallote Group Title
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    last i heard minimum value was in a calculus class o.O i never knew it was in algebra too

    • 2 years ago
  23. Lukecrayonz Group Title
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    It's in Algebra 2.

    • 2 years ago
  24. Lukecrayonz Group Title
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    You can use a calculator to solve it

    • 2 years ago
  25. samjordon Group Title
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    hahah its in math 11 here in canada

    • 2 years ago
  26. satellite73 Group Title
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    \[(-\frac{9}{2})^2+9\times (\frac{-9}{2})+18\] then a calculator if you need one

    • 2 years ago
  27. satellite73 Group Title
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    you turn math up to eleven in canada? mine only goes up to ten

    • 2 years ago
  28. Lukecrayonz Group Title
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    Ti-84, input the equation into Y= then click 2nd Trace, and do minimum. It will say "Left bound?", go to the left side of the graph and press enter. Right bound? Obviously, right side. It will say "Guess?", which means put it to where you think the minimum y value is.

    • 2 years ago
  29. Lukecrayonz Group Title
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    So for this, you get x=-4.5 and y=-2.25

    • 2 years ago
  30. tbrooks3 Group Title
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    sooo many numbers ... ahhhhh!!! >_< what about TI-83 plus?

    • 2 years ago
  31. samjordon Group Title
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    hahaha grade 11 math lol

    • 2 years ago
  32. lgbasallote Group Title
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    so taking the derivative and equating to zero is another story?

    • 2 years ago
  33. Lukecrayonz Group Title
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    It'll be exactly the same basically I think.

    • 2 years ago
  34. Lukecrayonz Group Title
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    Yes lgb haha

    • 2 years ago
  35. tbrooks3 Group Title
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    they give us this freshman yr. imma senior now tryna make it up.. sucks :/

    • 2 years ago
  36. tbrooks3 Group Title
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    thanks everyone

    • 2 years ago
  37. satellite73 Group Title
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    using the derivative to find the minimum value of a quadratic. like using a glock to kill a wingspanroach

    • 2 years ago
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