A community for students.

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

anonymous

  • one year ago

Solve 5x2 = -30x - 65.

  • This Question is Closed
  1. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    \[5x^2=-30x-65 \\ 5x^2+30x+65=0\] you could divide both sides by 5 and see if you end up with something factorable on the the left hand side or you can just use quadratic formula

  2. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i tried that and i wound up with \[\frac{ 6\pm \sqrt{-16} }{ -2}\]

  3. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    \[\text{ dividing both sides by 5} \\ x^2+6x+13=0\]

  4. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    \[x=\frac{-6 \pm \sqrt{6^2-4(1)(13)}}{2(1)} \\ =\frac{-6 \pm \sqrt{36-52}}{2}=\frac{-6 \pm \sqrt{-16}}{2} =\frac{-6 \pm \sqrt{-1(16)}}{2} \\ =\frac{-6 \pm \sqrt{-1} \sqrt{16}}{2}\] you are right so far

  5. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    just need to find sqrt(16) and just recall how we rename sqrt(-1)

  6. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    how did you get -1 in radical and 16 ?

  7. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    so 4? sqrt -1?

  8. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    a. x = -3 ± 2i b.x = -3 ± 4i c.x = -6 ± 2i d.x = -6 ± 4i These are the answers that I got and I'm so confused

  9. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    wait would it be d?

  10. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    \[=\frac{-6 \pm i (4)}{2} \\ =\frac{-6}{2} \pm i \frac{4}{2}\] can you simplify? Are you asking where I got sqrt(-16) didn't you also get that for that one part? That is what your expression said.

  11. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    oh so A i got it ! lol

  12. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    can you help me with this one as well ? Solve -3x2 + 30x - 90 = 0.

  13. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    try dividing both sides by -3 and use quadratic formula again

  14. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    lol hold on a baby stole my pen and paper lol

  15. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    oh no!

  16. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i got it back lol

  17. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    see how far you can get with the problem and if you can't get all the way through it post what you can get through

  18. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    ok

  19. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    k im stuck on almost the last part im at \[\frac{ -10\pm \sqrt{220} }{ 2 }\]

  20. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    let me check what you have so far one sec

  21. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    \[-3x^2+30x-90=0 \\ \text{ divide both sides by -3 just \to make things easier \to play with } \\ x^2-10x+30=0 \\ x=\frac{-(-10) \pm \sqrt{(-10)^2-4(1)(30)}}{2(1)}\]

  22. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    so -(-10)=10 and 100-120=-20

  23. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    \[x=\frac{10 \pm \sqrt{-20}}{2}\]

  24. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    now sqrt(-20)=sqrt(-1)*sqrt(20) but there is a perfect square factor in 20 sqrt(-20)=sqrt(-1)*sqrt(4)*sqrt(5)

  25. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    \[x=\frac{10 \pm \sqrt{-1} \sqrt{4} \sqrt{5}}{2}\] see if you can simplify from there

  26. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    is it this?x equals 10 plus or minus 2i square root of 5

  27. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    all over 2 right ?

  28. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    huh?

  29. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    \[x=\frac{ 10 \pm i (2)\sqrt{5}}{2}\] you didn't say anything about the 2 on bottom

  30. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    ohj yea

  31. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    anyways you can separate the fraction and simplify a bit more

  32. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    with the 10 and the 2?

  33. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    (A+B)/C=A/C+B/C so from previous we have: \[x=\frac{10}{2} \pm i \frac{2}{2}\sqrt{5}\]

  34. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    x equals 5 plus or minus i square root of 5?

  35. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yes since 10/2=5 and 2/2=1

  36. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    can you help me with the rest xDDD lol

  37. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i think i can help with one more but I want to see you work it all the way to the end and I will check it and we can make changes if needed

  38. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Solve 5x2 = -30x - 65.

  39. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    that is the same as the first equation you put

  40. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    but we can do it again if you didn't understand it

  41. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    oh lol i put the wrong one cx

  42. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Solve x2 + 4x + 8 = 0.

  43. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    since we already did this one I will be a bit more detailed with the explanation: \[5x^2=-30x-65 \\ \text{ I first added } 30x \text{ and } 65 \text{ on both sides } \\ 5x^2+30x+65=0 \\ \text{ I then notice all terms are divisible by 5} \\ \text{ So I divided both sides by 5} \\ x^2+6x+13=0 \\ \text{ comparing this to } ax^2+bx+c=0 \\ \text{ I identified } a=1, b=6,c=13 \\ \text{ so using the quadratic formula we have } \\ x=\frac{-b \pm \sqrt{b^2-4ac}}{2a}=\frac{-(6)\pm \sqrt{(6)^2-4(1)(13)}}{2(1)} \\ x=\frac{-6 \pm \sqrt{36-52}}{2} \\ x=\frac{-6 \pm \sqrt{-16}}{2} \\ \text{ now } \sqrt{-16}=\sqrt{-1(16)}=\sqrt{-1} \sqrt{16}=i (4)=4i \\ \text{ so we have } \\ x=\frac{-6 \pm 4i}{2} \\ \text{ now seperating the fraction } \\ x=\frac{-6}{2}\pm\frac{4i}{2} \\ x=\frac{-6}{2}\pm\frac{4}{2}i \\ x=-3 \pm 2i\] now I see you have another equation there see if you can follow what I did here to solve your equation

  44. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    you can skip to comparing your equation to ax^2+bx+c=0

  45. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    which I think your problem isn't identifying a,b, and c

  46. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    your problem is playing with the square root and separating the fraction

  47. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    \[x^2+4x+8=0 \\ \text{ is the same as } 1x^2+4x+8=0 \\ \\ a=1,b=4,c=8 \\ x=\frac{-b \pm \sqrt{b^2-4ac}}{2a}=\frac{-(4) \pm \sqrt{4^2-4(1)(8)}}{2(1)} \\\] what do you get when you simplify this monster (and he isn't a bad looking monster; just a few teeth)

  48. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    \[\frac{ -4\pm \sqrt{16-32} }{ 2 }\] so \[\frac{ -4\pm \sqrt{-16} }{ 2 }\] but im stuck now :/

  49. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    beautiful so far

  50. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    I actually simplify sqrt(-16) for you above

  51. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    would i divide the -16 by 4?

  52. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    sqrt(16)=4 sqrt(-1)=i you have sqrt(-16) though sqrt(-16) remember -16 is same as -1*16 so sqrt(-16)=sqrt(-1*16) =sqrt(-1)*sqrt(16) you should be able to identify sqrt(-1) as i and you should be able to simplify sqrt(16) since you know 4^2=16 (Where 4>0) then sqrt(16)=?

  53. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    so would it be x equals negative 4 plus or minus 2 I

  54. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    all over ?

  55. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    2

  56. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    oh wait and why 2?

  57. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    sqrt(16)=4 not 2

  58. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    cause it was all over two

  59. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    minus what i said

  60. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    \[x^2+4x+8=0 \\ \text{ is the same as } 1x^2+4x+8=0 \\ \\ a=1,b=4,c=8 \\ x=\frac{-b \pm \sqrt{b^2-4ac}}{2a}=\frac{-(4) \pm \sqrt{4^2-4(1)(8)}}{2(1)} \\ \\ x=\frac{-4 \pm \sqrt{16-32}}{2} =\frac{-4 \pm \sqrt{-16}}{2} \\ x=\frac{-4 \pm 4i }{2} \\ \text{ now separate the fraction and simplify a bit more }\]

  61. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    so \[-2\pm2i\]

  62. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yes

  63. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    since -4/2=-2 and 4/2=2 so yep \[x=\frac{-4}{2} \pm \frac{4}{2}i =-2 \pm 2i\]

  64. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i think i got the rest <3 thank you . now i gotta fill out some more job apps :/ ugh growing up sucks wish there was such thing as never land

  65. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    with peterpan remember those kids never get pizza

  66. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    that is true but i would find a way to create it xD

  67. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    thank you again!!

  68. myininaya
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    np :)

  69. Not the answer you are looking for?
    Search for more explanations.

    • Attachments:

Ask your own question

Sign Up
Find more explanations on OpenStudy
Privacy Policy

Your question is ready. Sign up for free to start getting answers.

spraguer (Moderator)
5 → View Detailed Profile

is replying to Can someone tell me what button the professor is hitting...

23

  • Teamwork 19 Teammate
  • Problem Solving 19 Hero
  • You have blocked this person.
  • ✔ You're a fan Checking fan status...

Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.

This is the testimonial you wrote.
You haven't written a testimonial for Owlfred.