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Weekly maths challenge...

Discussion in 'Off Topic' started by Liam W, Oct 4, 2013.

  1. Liam W

    Liam W Well-Known Member

    I've added this to my signature...

    Got the solution? I'm doing it in school...
     
  2. Martok

    Martok Well-Known Member

    Yep, got the solution but just in case this is one of your school problems I'd best not give you the answer. ;)

    All I will say is complex numbers, nice. :)
     
  3. Liam W

    Liam W Well-Known Member

    I literally made it up on the spot while typing it out into the signature box :p

    I better had complete it now, so I know if other's get it right!
     
  4. Martok

    Martok Well-Known Member

    Oh OK, I believe you. ;)

    x=i-1
    or if you prefer it written 'correctly' as a complex number,
    x=-1+i
     
  5. The Forum Heroes

    The Forum Heroes Well-Known Member

    x=42 Everything always equals 42
     
    principia and Amaury like this.
  6. Digital Doctor

    Digital Doctor Well-Known Member

  7. Digital Doctor

    Digital Doctor Well-Known Member

    What's i ?
    :)
     
  8. Amaury

    Amaury Well-Known Member

    A variable.
     
  9. Martok

    Martok Well-Known Member

    i is the square root of -1.
     
  10. RobParker

    RobParker Well-Known Member

    Isn't it actually x = -1 +/- i?

    Liam, I assume you're doing quadratic equations at school?

    Set the two expressions you've been given as being equal (as you're told in the question) and then get it into the form 0 = ax^2 + bx + c

    The use the quadratic formula to get the value of x.
     
  11. Martok

    Martok Well-Known Member

    Yes, you are correct,
    x=-1+i
    and
    x=-1+i

    because of course sqrt of -1 is indeed either -i or +i
     
  12. RobParker

    RobParker Well-Known Member

    Erm no...I actually meant because the quadratic formula is (-b +/- sqrt(b^2-4ac))/2a. You only did the + part of that.
     
  13. Martok

    Martok Well-Known Member

    Yes of course! Though (-i)^2 and i^2 both equal sqrt -1, you are correct that it is from the quadratic equation that you get both of the answers for x. :)

    *EDIT* Actually were both correct. You just did it using the quadratic formula to calculate the answer. I did it from the quadratic equation and resolving as far as x=-1 + sqrt(-1) I just forgot that sqrt(-1) has two answers, -i and +i. What the quadratic formula reminds us of is that there are two answers to any sqrt, the positive and the negative hence ± in the formula. :)
     
    Last edited: Oct 4, 2013
    RobParker likes this.
  14. Chris D

    Chris D XenForo Developer Staff Member

    I've given this a lot of thought and I've come to the conclusion that x = bacon.
     
    Jeremy, Liam W, Teapot and 3 others like this.
  15. Tracy Perry

    Tracy Perry Well-Known Member

    That's easy... x = the 24th letter of the english alphabet. :p
     
  16. mistypants

    mistypants Well-Known Member

    Oh man, I don't miss Calculus. So glad I'm almost done with my math credits.
     
    Amaury likes this.
  17. Liam W

    Liam W Well-Known Member

    Well done all :)

    I did this on paper last night... I forgot to change the minus to a plus on the 10 when transferring it over :(

    Solution:

    5x^2+12x = 2(x-5)

    5x^2+12x = 2x-10

    5x^2+12x-2x+10=0

    5x^2+10x+10=0

    x=-b±sqrt(b^2-4ac)/2a

    x=-10±sqrt(10^2-4x5x10)/2x5

    x=-10±sqrt(100-200)/10

    x=-10±sqrt(-100)/10

    x=-10+sqrt(-100)/10 OR x=-10-sqrt(-100)/10

    x=-10+10i/10 or x=-10-10i/10

    x=-1+i or x=-1-i
     
  18. RobParker

    RobParker Well-Known Member

  19. BirdOPrey5

    BirdOPrey5 Well-Known Member

    While I liked math, can't say I miss this stuff. I can say I have never had to do a quadratic equation in the 10 years I spent as a project engineer, then director of engineering. (Or 5 years since.)
     
  20. CyclingTribe

    CyclingTribe Well-Known Member

    I'll be honest and say I've absolutely no idea whatsoever ... :D
     

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