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Rauhan Dec 30, 2017
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Question 1

 

a)     f( x )  =  3x2 - 5x + 6    and    g(x)  =  x2 + 3x

 

f o g   =   f( g(x) )

 

f o g   =   f( x2 + 3x )

 

f o g   =    3( x2 + 3x )2 - 5( x2 + 3x ) + 6    I'll let you simplify these if necessary...

 

The domain is (-∞, ∞), and from this graph, we can see that the range is  [47/12, ∞) .

 

g o f   =   g( f(x) )

 

g o f   =  g( 3x2 - 5x + 6 )

 

g o f   =   ( 3x2 - 5x + 6 )2 + 3( 3x2 - 5x + 6 )

 

The domain is  (-∞, ∞), and from this graph, we can see that the range is  [3901/144, ∞) .

 

 

b)     f(x)  =  2x    and    g(x)  =  3 - x

 

f o g   =   f( g(x) )

 

f o g   =   f( 3 - x )

 

f o g   =   23 - x

 

The domain is  (-∞, ∞), and the range is  (0, ∞) .

 

g o f   =   g( f(x) )

 

g o f   =   g( 2x )

 

g o f   =   3 - 2x

 

The domain is  (-∞, ∞), and the range is  (-∞, 3) .

 

 

c)     f(x)  =  sin x    and    g(x)  =  x

 

f o g   =   f( g(x) )

 

f o g   =   f(  x  )             We already know that  f(x)  =  sin x , so....

 

f o g   =   sin x

 

The domain of this is  (-∞, ∞), and the range is  [-1, 1] .

 

g o f   =   g( f(x) )

 

g o f   =   g( sin x )     Plug in  " sin x "  for  " x "  into the function  g(x) .

 

g o f   =   sin x

 

The domain is  (-∞, ∞),  and the range is  [-1, 1] .

hectictar Dec 30, 2017

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