## Renee99 3 years ago How can you tell when a quadratic equation has no real solutions? A. when the radicand is negative B. when b in the quadratic formula is greater than the radicand C. when the radicand equals zero D. when the radicand is not a perfect square I believe the answer is A? is that right?

1. Mertsj

A

2. campbell_st

its A using the discriminant $b^2 - 4ac$ < 0 no real solutions the radical will be negative

3. experimentX

4. experimentX

i go with campbell

5. campbell_st

the square root symbol

6. Mertsj

b^2-4ac

7. Mertsj

$x=\frac{-b \pm \sqrt{b^2-4ac}}{2a}$

8. Renee99

Thanks!! :) I also have this one... For which value of x does the graph of y = 2x2 − 7x + 6 cross the x-axis? A. −3/2 B. −2/3 C. 2 D. 3 I think its C.

9. Mertsj

$b^2-4ac$ is the discriminant

10. Mertsj

You are correct.

11. campbell_st

you can substitute each value to find y = 0 or factorise (2x - 3)(x - 2) = 0 x = 3/2 and 2

12. Renee99

Thanks so much, here's another one i'm stuck on... What are the approximate solutions of 4x2 + 3 = −12x to the nearest hundredth? A. x ≈ −3.23 and x ≈ 0.23 B. x ≈ −2.72 and x ≈ −0.28 C. x ≈ 0.28 and x ≈ 2.72 D. x ≈ −0.23 and x ≈ 3.23 I think its C, but I'm not sure??

13. campbell_st

put it in standard form 4x^2 + 12x + 3 = 0 use the general quadratic formula $x = (-b \pm \sqrt{b^2 - 4ac})/2a$ in your question a = 4, b = 12 and c = 3

14. Mertsj

C is correct.

15. Renee99

thanks so much!! :)

16. Mertsj

No. It's B

17. Mertsj

Both roots are negative.

18. Renee99

B? Really? are you sure?

19. Renee99

Okay, i'll trust you! :)

20. Mertsj

$x=\frac{-12\pm \sqrt{96}}{8}$

21. Renee99

I have one more question that's really confusing me, would you mind sticking around for one more?

22. Mertsj

$x=\frac{-12+9.80}{8} or x=\frac{-12-9.80}{8}$

23. Mertsj

ok

24. Renee99

*note* don't ask me why the numbers are spreed out like that, I just copied and pasted it onto here, that how it looks on my paper. Which part of the quadratic formula tells you whether the quadratic equation can be solved by factoring? −b b2 − 4ac 2a Use the part of the quadratic formula that you chose above and find its value given the following quadratic equation: 2x2 + 7x + 3 = 0

25. Mertsj

b^2-4ac

26. Renee99

27. Mertsj

Well which part would you choose? -b? 2a????

28. Mertsj

$b^2-4ac=7^2-4(2)(3)=49-24=25$

29. Renee99

I don't know... This is really confusing me for some reason...

30. Renee99

31. Renee99

I'm still confused... :/

32. Renee99

or is the answer this: b² - 4ac = (7)² - 4(2)(3) = 49 - 24 = 25.

33. Mertsj

The discriminant, which is b^2-4ac, is the part of the quadratic formula which tells you about the roots.

34. Mertsj

Do you understand that the question has two parts? READ THE QUESTION!!!

35. Mertsj

PART 1: Which part of the quadratic formula tells you whether the quadratic equation can be solved by factoring?

36. Mertsj

The answer to that is :b^2-4ac

37. Mertsj

PART 2: Use the part of the quadratic formula that you chose above and find its value given the following quadratic equation: 2x2 + 7x + 3 = 0

38. Mertsj

The answer to that is 25

39. Renee99

ohhh okay, I understand now

40. Renee99

Thank you!!

41. Mertsj

yw

42. Renee99

I just wasn't looking at the problem correctly, sorry for the confusion and thanks again for breaking it down for me