I'm completely lost, so if you show how you've done it step by step that would be nice :D
\(0 = {-2r^2 - 6r }\)
+128475 -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)
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