Application in Set Theory

  • Thread starter mtayab1994
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  • #1
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Polynomial Function.

Homework Statement



f:ℝ→ℝ
x→x^2+x+2

Homework Equations



Prove that: f(ℝ)=[7/4,+∞[

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:

Answers and Replies

  • #2
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What is the minimum value of x2+x+1?
 
  • #3
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the minimum value for x^2+x+1 is obviously 1
 
  • #4
HallsofIvy
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If x=-1/2, [itex]x^2+ x+ 1= 1/4- 1/2+ 1= 3/4[/itex]. Try thinking before reacting!
 
  • #5
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If x=-1/2, [itex]x^2+ x+ 1= 1/4- 1/2+ 1= 3/4[/itex]. Try thinking before reacting!
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
 

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