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f(x)=3-√x and g(x)=5x+2x^2, what is f(g(-5))?

 May 21, 2019
 #1
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nvm my mistake was found, it is -2

 May 21, 2019
 #2
avatar+19897 
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First find  g(5)  by putting in 5 for x  

 

5(-5) + 2 (-5)^2 = -25 + 50 = 25

 

then put 25 in f(x)

 

3 - sqrt(25) = 3 - 5 = -2      (it COULD be  (3 - -5) = 8    because sqrt 25 is +-5 )   

 May 21, 2019
 #3
avatar+8842 
+3

\(\sqrt{25}\)  equals only  5

 

\(\pm\sqrt{25}\)   equals  ± 5

 

See: https://en.wikipedia.org/wiki/Radical_symbol#Principal_square_root

hectictar  May 21, 2019

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