+0  
 
+1
97
1
avatar+545 

https://vle.mathswatch.co.uk/images/questions/question15425.png

 

 

winkwinkwink

lynx7  Apr 12, 2018
 #1
avatar+87639 
+2

3(x + 1) (x + 7)  - (2x + 5)^2  simplify

 

3 (x^2 + 8x + 7) - (2x + 5)(2x + 5)

 

3x^2 + 24x + 21 - [ 4x^2 + 20x + 25 ]

 

-x^2 + 4x - 4

 

The x coordinate of vertex of this function  is given by :

 

-4/ (2 (-1) )   =  4/2  = 2

 

And the max value of this function  is  :

 

-(-2)^2 + 4(2) - 4   =  -4 + 8 - 4  =   0

 

So....this function is never positive

 

cool cool cool

CPhill  Apr 12, 2018

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