## mathhelp23 3 years ago solve 3x^2-5x-11=0 find the x intersepts of f(x)=3x^2-5x-11.

1. Hero

It's not complex

2. Hero

$D = b^2 - 4ac = (-5)^2 - 4(3)(-11) = 25 + 132 = 157$

3. Hero

$x = \frac{\pm \sqrt{157} + 5}{6}$

4. mathg8

any method ?

5. mathhelp23

thank you

6. krypton

@Hero that's the answer i got,dat's why i called it a complex root

7. mathg8

@krypton : square root of a negative number gives you a complex number solution

8. myininaya

any number is complex

9. myininaya

4 is complex 4i is complex 4+4i is complex

10. mathg8

4+0i

11. mathg8

why do we have real and complex sets then ?

12. myininaya

real numbers is a subset of the complex imaginary numbers is a subset of the complex

13. myininaya

all numbers are complex

14. mathg8

If a complex number has b = 0, then it is a real number and it lies on the real axis in the complex plane

15. myininaya

Definition of Complex: $Complex =\{a+bi | a \in \mathbb{R} , b \in \mathbb{R}\}$

16. Hero

Define complex in words only without using mathematical notation.

17. Hero

What a meant to say is that the discriminant yields a real number, not a complex number. The definition of a complex number is a + bi

18. mathg8

The real line can be thought of as a part of the complex plane, and correspondingly, complex numbers include real numbers as a special case.

19. mathg8

... Special Case

20. Hero

That's good to know. I'm not the one confused about it.

21. myininaya

Excuse me?

22. myininaya

I'm not confused either.

23. Hero

I know you're not myininaya. I never said you were :P

24. mathg8

def : A complex number is neither purely real nor purely imaginary, but rather is a composite of the two ! Happy everyone ?

25. myininaya

Ok I guess I just understood you. sorry hero. :)

26. myininaya

misunderstood you* lol

27. myininaya

real numbers are complex imaginary numbers are complex real numbers+imaginary numbers are still complex

28. Hero

she avoided using the word "pure" in her definitions.

29. myininaya
30. Hero

So myininaya, which numbers are purely complex?

31. myininaya

I don't have a definition for "purely" complex numbers as I never heard of any set of numbers being defined at such sorry

32. mathg8

check out this book : An imaginary tale The Story of √-1 by Paul J. Nahim ( Professor Emeritus of Electrical Engineering at the University of New Hampshire )

33. Hero

Guess there's no such thing as a pure complex number since it is a "mixture" of pure real and pure imaginary.

34. mathg8

4 is real 4+0i is complex

35. myininaya

4=4+0i

36. myininaya

4/2 is an integer just like 2 is

37. myininaya

because 4/2=2

38. myininaya

@jamesj @zarkon

39. Hero

Why are you two reciting stuff you already know? Because I already know this stuff

40. mathg8

|dw:1331351848500:dw|

41. mathg8

this is interesting ... LOL

42. Hero

mathg8, I guess you really want krypton to understand

43. mathg8

I just never heard this before ... so it is interesting ( not wrong or right ) just interesting ...

44. mathg8

real numbers are complex ( i meant this statement )

45. krypton

lol intresting :)

46. Hero

Krypton, I'm sure you enjoyed this

47. krypton

lol yeah! alot,just woke up from sleep and logged in,only to find some argument in here.was fun :)

48. mathg8

yes ... this was fun!