1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: OH NO! A few problems

  1. Mar 9, 2005 #1

    see if any of you guys can solve a few of these.. if you guys can show me the steps so that i can study them for any of my future tests that would be great. :eek:
  2. jcsd
  3. Mar 9, 2005 #2
    16. Do you know what a parabola is?? Do you know what a vertex is???

    17. Can you complete the square???

    18. This is more of trial and error than a formula.

    19. Pretend the 'more than or equal to' sign is an equal sign and then solve.

    20. Can you use the quadratic equation or factorise???

    If you know any of this I can start to help, if not I need to explain it. :smile:

    The Bob (2004 ©)
    Last edited: Mar 9, 2005
  4. Mar 9, 2005 #3
    nope. i have no idea what im doing.

    edit: actually, i know what a vertex is.

    i dont know what a parabola is though :bugeye:
    Last edited: Mar 9, 2005
  5. Mar 9, 2005 #4
    A parabola is what you get when you draw the function y = x2. Do you know what that looks like???

    Lets say you have x2 - 6x + 10. Completing the square would make the equation like this: (x - 3)2 + 10 - 9 = (x - 3)2 + 1. All that has happened is the -6x has been halved and put in brackets and then the new number (-3) has been squared and taken away from the 10.

    Try completing the sqaure of x2 - 10x + 30. Completing the sqaure is also needed for 19.

    18. I would use the quadratic forumla : [tex]\frac{-b \pm \sqrt{b^2 - 4ac}}{2a}[/tex] but I think it will want you to complete the square.

    Question 20 can be factorise from 2x2 - 7x - 15 = 0 to (2x + 3)(x - 5) = 0 and then you have some values to use.

    The Bob (2004 ©)
    Last edited: Mar 9, 2005
  6. Mar 9, 2005 #5
    I need to go sleep now but here are some completing the square question, for you, for practise and I am sure someone else will say if they are right or wrong for you:

    y = x2 - 8x + 20
    y = x2 - 4x + 7
    y = x2 + 2x + 2
    y = x2 + 4x + 2
    y = x2 - 10x + 25

    Good Luck and I will read what you have done tomorrow. :smile:

    The Bob (2004 ©)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook