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I forgot How to do these

  1. Jan 20, 2008 #1
    I forgot How to do these....

    1. The problem statement, all variables and given/known data

    y = x^2 - 8x + 10
    change into y = (x[plus or minus]A)*(x[plus or minus]B)

    I just forgot how to do these.... real fast could someone solve w/ showing work?

    Thanks. I just don't remember how to do it.....
     
  2. jcsd
  3. Jan 20, 2008 #2
    You need to find 2 numbers that give you the difference of -8 and the product of positive 10.

    Since you won't be able to find it by simple factorization, you have to use the quadratic formula.

    Google is your friend!
     
  4. Jan 20, 2008 #3
    Oh ok thanks.

    yea, i was just running factors over and over in my head and i wasn't coming up with anything, I'm kind of brain dead, so i wasn't sure if it was just me. Thanks.
     
  5. Jan 20, 2008 #4
    1 and 10
    2 and 5

    :(
     
  6. Jan 20, 2008 #5
    when i type in on Google quadratic formula, then i plug the equations in, it tells me x=16 and x = 8

    ?????? not the answer i need.
     
  7. Jan 20, 2008 #6
    also those were wrong, i did it wrong. hold on
     
  8. Jan 20, 2008 #7
    Nope ... try it again.
     
  9. Jan 20, 2008 #8
    ok i think i got it, is it just (x - [8+[tex]\sqrt{24}[/tex]/2]) * (x - [8-[tex]\sqrt{24}[/tex]/2])?
     
  10. Jan 20, 2008 #9
    Yes, but don't forget to reduce!
     
  11. Jan 20, 2008 #10
    by that, you just mean plugging it into a calculator and finding the answer, correct?

    which happens to be 6.5505 & 1.4495 correct?
     
  12. Jan 20, 2008 #11
    No. [tex]\frac{8 \pm \sqrt{4 \cdot 6}}{2}[/tex] can reduce.
     
  13. Jan 20, 2008 #12
    so 4 [tex] \pm \sqrt{2*3} [/tex]?
     
  14. Jan 20, 2008 #13
    Yeppp.
     
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