## ksaimouli 4 years ago x^2-x+1/x-3 find x intercpts

1. amistre64

this thing only is zero when the top is zero

2. ksaimouli

could u show plz

3. amistre64

show you ... what? how to plug values into the quadratic formula? im assuming you know the formula that is

4. ksaimouli

|dw:1327858303543:dw|

5. ksaimouli

nope

6. amistre64

$ax^2+bx+c=0$ $x=\frac{1}{2a}(-b\pm\sqrt{b^2-4ac})$

7. amistre64

which is what completing the square proves ....

8. ksaimouli

yes i know this but i dont know hoew to slove this

9. amistre64

if you know this, then you DO know how to solve this. so whre is the issue?

10. ksaimouli

nope i dont know how to slove

11. ksaimouli

i just know the formula

12. amistre64

x^2-x+1 define a, b, and c for me from this

13. ksaimouli

i will draw ok

14. amistre64

if drawing helps, by all means :)

15. ksaimouli

|dw:1327858568209:dw|

16. amistre64

thats correct so far.

17. myininaya

is it?

18. myininaya

|dw:1327858704164:dw|

19. amistre64

$\frac{--1\pm\sqrt{(-1)^2-4(1)(1)}}{2(1)}$ i was assuming a typo lol

20. ksaimouli

|dw:1327858744957:dw|

21. amistre64

$\frac{--1\pm\sqrt{(-1)^2-4(1)(1)}}{2(1)}$ $\frac{1\pm\sqrt{1-4}}{2}$ $\frac{1\pm i\sqrt{3}}{2}$

22. ksaimouli

what is i

23. amistre64

i is a complex number meaning that this has no "real" number solutions

24. amistre64

i = $$\sqrt{-1}$$

25. ksaimouli

so what is x inter

26. myininaya

there exist no x-intercept if you have an imaginary solution to f=0

27. amistre64

there are no "real" x intercepts, you have a parabola type thing that never touches the x axis

28. ksaimouli

ok so no x interscpts if it does not simplyfy

29. amistre64
30. ksaimouli

so when we should use the quadratic formula ?

31. amistre64

if you get complex numbers; which is a sqrt(-#) then its not going to ever get intercepted by the x axis

32. amistre64

always

33. myininaya

when you are solving for x and the equation has this form $ax^2+bx+c=0$ or can be written in that form

34. amistre64

just know that there are 3 ways that an outcome can occur

35. myininaya

one x-intercept if b^2-4ac=0 two x-intercepts if b^2-4ac>0 no x-intercepts if b^2-4ac<0

36. amistre64

b^2-4ac = - , no real xints b^2-4ac = 0, 1 real xint b^2-4ac = +, 2 real xints

37. amistre64

i spose i gotta down the chrome; ies slowing up big time

38. ksaimouli

ok i got u what in this case -2x^2-2x-3/x

39. ksaimouli

x interce

40. myininaya

just needed a refresh you do the same thing by the way that -2x^2-2x-3 is the top right?

41. ksaimouli

yup

42. ksaimouli

we cant factor right

43. myininaya

just plug into the formula amistre gave you

44. myininaya

factor? There are no two factors of -2(-3)=6 that have product 6 and add up to be -2

45. ksaimouli

i will plug and give u answer u say me is it right or wrong ok @ mi

46. myininaya

i will be back after you answer

47. ksaimouli

ok 1+0r-root(4-24)/-4

48. ksaimouli

|dw:1327859584777:dw|

49. myininaya

$x=\frac{-(-2) \pm \sqrt{(-2)^2-4(-2)(-3)}}{2(-2)}=\frac{2 \pm \sqrt{4-24}}{-4}=\frac{2 \pm \sqrt{-20}}{-4}$ This can be simplified further

50. ksaimouli

after that

51. myininaya

|dw:1327859739220:dw|

52. myininaya

you only made one mistake so far so that is pretty good

53. ksaimouli

i have to find xinter right

54. myininaya

there is no x intercept -20 is a negative number

55. ksaimouli

ok got u thx u very mucj @myini