+0  
 
0
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I'm completely lost, so if you show how you've done it step by step that would be nice :D

\(0 = {-2r^2 - 6r }\)

Guest Jan 31, 2018
 #1
avatar+87639 
+1

-2r^2  - 6r   =  0

Factor out the -2

 

-2 ( r^2  + 3r )  =  0

 

We are going to complete the square on  "r"

 

Take   1/2 of 3   =  3/2    .....square it  =9/4.....add and subtract it inside the parentheses....so we have...

 

-2 ( r^2  + 3r  +  9/4   -  9/4)        factor the first three terms

 

-2 [  (  r + 3/2)^2  - 9/4)  ]      distribute the -2 over each term in the parentheses

 

-2(r + 3/2)^2  +  18/4

 

-2(r + 3/2)^2  +  9/2

 

This is vertex form

 

The vertex  is  (-3/2,  9/2)

 

 

cool cool cool

 

 

 

 

 

-

CPhill  Jan 31, 2018

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