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iwanttogotostanford
 one year ago
HELP PLEASE IM STUCK:
Using the completingthesquare method, find the vertex of the function f(x) = –2x^2 + 12x + 5 and indicate whether it is a minimum or a maximum and at what point.
Maximum at (–3, 5)
Minimum at (–3, 5)
iwanttogotostanford
 one year ago
HELP PLEASE IM STUCK: Using the completingthesquare method, find the vertex of the function f(x) = –2x^2 + 12x + 5 and indicate whether it is a minimum or a maximum and at what point. Maximum at (–3, 5) Minimum at (–3, 5)

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jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.0Vertex form is \(\Large y = a(xh)^2+k\) The vertex of that equation is \(\Large (h,k)\) From \(\Large 2x^2 + 12x + 5\) we see that \(\Large a = 2, b = 12, c = 5\) Plug the values of 'a' and 'b' into the formula \[\Large h = \frac{b}{2a}\] to find the value of h. Tell me what you get

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Oh, I thought you already know the answer to this. Hmmm.

iwanttogotostanford
 one year ago
Best ResponseYou've already chosen the best response.0so it would be A? @jim_thompson5910

iwanttogotostanford
 one year ago
Best ResponseYou've already chosen the best response.0because it increases

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.0you're looking at the graph I'm guessing?

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.0do you know how to determine without the graph? by just looking at the value of 'a'

iwanttogotostanford
 one year ago
Best ResponseYou've already chosen the best response.0no, but can you just determine by looking at the graph?

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.0well let's say we don't have a graphing calculator since 'a' is a negative number, this means that the parabola opens downward like this dw:1442446419996:dw a good way to remember this is to think "The value of 'a' is negative. Negative means sad, so we have a sad face graph"

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.0and of course, at the peak of this "sad face graph" is the vertex. Which in this case, is the max dw:1442446478716:dw

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.0do you know how to find h and k without graphing?

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.0use the formula I posted earlier use h = b/(2a)

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.0plug in a = 2 and b = 12 into that formula what is the value of h?

iwanttogotostanford
 one year ago
Best ResponseYou've already chosen the best response.0the value of H would be 3 right?

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.0yes, let's do another example Let's say we had y = 3x^230x+85 what are the values of a,b,c ? what is the value of h?

iwanttogotostanford
 one year ago
Best ResponseYou've already chosen the best response.0a=3x^2 b=30 c=85 and then h would be 30/18? i think i got it wrong...

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.0a,b,c are just numbers (no variables attached)

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.0a = 3, b = 30, c = 85

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.0To find h, we do this \[\Large h = \frac{b}{2a}\] \[\Large h = \frac{(30)}{2*3}\] \[\Large h = ???\]

iwanttogotostanford
 one year ago
Best ResponseYou've already chosen the best response.0can you give me one second? please just one minute:)

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.0Take all the time you need. There's no rush.

iwanttogotostanford
 one year ago
Best ResponseYou've already chosen the best response.0ok, so i worked it out and found that it was B

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.0I'm asking for a number

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.0if you plug a = 3 and b = 30 into that h formula, what result do you get?
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