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Algebra of Functions

If two functions have a common domain, then arithmetic can be performed with them using the following definitions.




Example 1: If f ( x) = x + 4 and g( x) = x2 − 2 x − 3, find each of the following and determine the common domain.




The common domain is {all real numbers}.




The common domain is {all real numbers}.




Use the distributive property.




The common domain is {all real numbers}.




This expression is undefined when x = 3 or when x = −1. So the common domain is {all real numbers except 3 or −1}.

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