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By evaluate we mean one of two things depending on what is in the parenthesis. If there is a
number in the parenthesis then we want a number. If there is an x (or no parenthesis, since that
implies and x) then we will perform the operation and simplify as much as possible.
(a) ( f + g ) ( 4) In this case we’ve got a number so we need to do some function evaluation. ( f + g ) ( 4) = f ( 4) + g ( 4)
= ( 2 + 3 ( 4 ) - 42 ) + ( 2 ( 4 ) - 1)
= -2 + 7
=5 [Return to Problems] © 2007 Paul Dawkins 190 http://tutorial.math.lamar.edu/terms.aspx College Algebra (b) g - f
Here we don’t have an x or a number so this implies the same thing as if there were an x in
parenthesis. Therefore, we’ll subtract the two functions and simplify. Note as well that this is
written in the opposite order from the definitions above, but it works the same way. g - f = g ( x) - f ( x) = 2 x - 1 - ( 2 + 3x - x 2 )
= 2 x - 1 - 2 - 3x + x 2
= x2 - x - 3 (c) [Return to Problems] ( fg ) ( x ) As with the last part this has an x in the parenthesis so we’ll multiply and then simplify. ( fg ) ( x ) = f ( x ) g ( x ) = ( 2 + 3 x - x 2 ) ( 2 x - 1)
= 4 x + 6 x 2 - 2 x3 - 2 - 3x + x 2
= -2 x 3 + 7 x 2 + x - 2 [Return to Problems...
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This note was uploaded on 06/06/2012 for the course ICT 4 taught by Professor Mrvinh during the Spring '12 term at Hanoi University of Technology.
- Spring '12