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If we express $3x^2 + x - 4$ in the form $a(x - h)^2 + k$, then what is $k$?

 Oct 20, 2017
 #1
avatar+98125 
+2

3x^2 + x - 4      factor out the 3

 

3 [x^2 +  (1/3)x - (4/3) ]

 

Take (1/2) of (1/3)  = 1/6.......square this = 1/36......add it and subtract it

 

3 [ x^2 + (1/3)x  + 1/36 - (4/3) - 1/36 ]   factor the first 3 terms

 

3 [ ( x + 1/6)^2 - 1/36 - 48/36 ]

 

3 [ (x + 1/6)^2 - 49/36 ]

 

3(x + 1/6)^2 - 49/12

 

So k =  -49/12

 

 

cool cool cool

 Oct 20, 2017
 #2
avatar+1442 
+1

Thank you so much I was struggling with completing the square now I get it

 Oct 20, 2017

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