A community for students.

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

anonymous

  • one year ago

Solve this please! Will medal for giving an answer!!! 0=-2x^2+11x+40

  • This Question is Closed
  1. ganeshie8
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 2

    Hint : (16)(-5) = -80 16 + -5 = 11

  2. ganeshie8
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 2

    As a start, split the middle term as `16x - 5x`

  3. ganeshie8
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 2

    0 = -2x^2 + `11x` + 40 = -2x^2 + `16x-5x` + 40

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

    wow i would have never thought of that!

  5. ganeshie8
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 2

    knw how to finish it off ?

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

    how did you figure that out?

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

    yeah i can finish it off but i'm intrigued on how you found those numbers

  8. ganeshie8
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 2

    basically we need to find two integers such that they multiply to `(40)*(-2)` and add up to the coefficient of middle term `11`

  9. ganeshie8
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 2

    so you look at the factors of 40*2 : 40*2 = 10*4*2 = 5*2^4 = 5*16 and you see that 16 and -5 are the magic numbers

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

    Wow thanks so much!

  11. ganeshie8
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 2

    quadratic formula is always there if you don't like to do all that

  12. ganeshie8
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 2

    |dw:1440046082224:dw|

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

    yeah of course I know that, haha

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

    but It seemed like there was a shorter way so I asked

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

    But really appreciate your work.

  16. ganeshie8
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 2

    im not sure if we can say that factor by grouping is any shorter than using the quadratic formula directly... factor by grouping doesn't work always, it works only when the roots are rational

  17. ganeshie8
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 2

    usually i try factor by grouping first, if it doesn't work then i use quadratic formula..

  18. 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.