How to find the domain of a Function (Multiple Examples)

 Radical Function Equation  (Let's find the domain) for f(x) = √5-x
  1. SET 5-X  ≥ 0 (Greater than or equal to zero)
  2. Solve for X   
  • 5-X  ≥ 0     SUBTRACT 5 ON BOTH SIDES
  • -X  ≥ -5      DIVIDE BY COEFFICIENT OF X, -1.
  • X ≤ 5         X AND 5 BECOME POSITIVE AND FLIP YOUR SIGN TO X ≤ 5 
  • (-∞, 5]       Domain is negative infinity to 5 closed bracket

  
Polynomial Function equation g(x)= x^2 +3x+1

  • your domain is all real numbers for any number for (x) can give you any answer, both negative and positive. (-∞,∞).

Fraction function f(x)= 2x+1/ x+5

  • x+5 ≠ 0      SET DENOMINATOR TO X CANNOT EQUAL 0 (X≠ 0 )
  • X ≠ -5        Solve for x, subtract 5
  • (-∞, -5)∪(-5,∞,)    Domain is all real numbers not including -5
Fraction function with square root as denominator g(x)= x^2 +2x+3/ √x+1
  • √x+1 > 0    SET DENOMINATOR GREATER THAN 0 (>0)
  • X+1 > 0     SOLVE FOR X
  • X>-1          SUBTRACT 1
  • [-1, ∞)       DOMAIN IS -1 TO POSITIVE INFINITY

Comments

  1. UnknownFebruary 19, 2018 at 7:06 AM

    I do a lot of math and this very useful to me to review some of my math concepts and for anyone who needs help in math. although some people may not understand why you figure out the equation this way and you should add some details on why is it solved this way and what does it mean. I personally learn better when I understand why the process is done the way it's done and it sticks to me better.

    ReplyDelete
  2. HAJMarch 15, 2018 at 4:04 PM

    You would be right to question my authority on these topics, or to accurately judge the usefulness of this equation. So all I can really judge this on is how well-suited it is to its audience and its medium. How well does this blog address its audience and purpose?

    While, this seems to be a pretty clear How-To for anybody needing to do maths, what makes it stand out from instructions in a textbook? What do these equations do? Are there any common errors that people should be aware of?

    Ultimately, while the clarity of the steps may be clear to anybody in the midst of a particular math class, there is not enough context to give this blog meaning to anybody except people doing their homework (and you don't even address them directly).

    Steps to improve this blog would be an explanation of what this equation is used for, common errors, and further explanation of the steps, probably.

    ReplyDelete

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