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: Application in Set Theory

  1. Oct 25, 2011 #1
    Polynomial Function.

    1. The problem statement, all variables and given/known data

    f:ℝ→ℝ
    x→x^2+x+2

    2. Relevant equations

    Prove that: f(ℝ)=[7/4,+∞[

    3. The attempt at a solution

    Well I don't know how answer this, so can someone give me a clue on how to start it off?
     
    Last edited: Oct 25, 2011
  2. jcsd
  3. Oct 25, 2011 #2
    What is the minimum value of x2+x+1?
     
  4. Oct 25, 2011 #3
    the minimum value for x^2+x+1 is obviously 1
     
  5. Oct 25, 2011 #4

    HallsofIvy

    User Avatar
    Science Advisor

    If x=-1/2, [itex]x^2+ x+ 1= 1/4- 1/2+ 1= 3/4[/itex]. Try thinking before reacting!
     
  6. Oct 26, 2011 #5
    Yea thanks for the tip i already tried it out yesterday and i figured it out.

    Once i stated that x=-1/2 then i get x^+x+2=7/4
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook




Loading...