PSAT Math : How to find the domain of a function

Study concepts, example questions & explanations for PSAT Math

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Example Questions

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Example Question #4 : Algebraic Functions

Find the domain of the function:

Possible Answers:

All real numbers

All real numbers except for –2

All real numbers except for 1


Correct answer:

All real numbers except for 1


If a value of x makes the denominator of a equation zero, that value is not part of the domain. This is true, even here where the denominator can be "cancelled" by factoring the numerator into

and then cancelling the  from the numerator and the denominator. 

This new expression,  is the equation of the function, but it will have a hole at the point where the denominator originally would have been zero. Thus, this graph will look like the line  with a hole where , which is 


Thus the domain of the function is all  values such that 

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