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functions question

Let f(x)=3x-1 and g(x)=x^2+4
 
find (f g)(-2)

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Is it (f+g)(-2), (f-g)(-2) or (f o g)(-2)?
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1 Answer

f(x ) = 3X -1     g( x ) = X^2 +4
 
  ( f +g) ( -2 )= [( 3(-2)  -1 +(-2^2)  + 4] =
                     = ( -6 - 1 +4 +4 ) = 1
 
  ( f - g ) ( -2) = [ 3(-2) -1 - ( -2^2 +4 ) ]=
                     = ( -7 -8) = -15
 
  (f ° g ) (-2 ) = [ 3 (-2^2 + 4) - 1 ] =
 
                    =  3( 8) - 1 = 23