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anonymous
 one year ago
Math help!
anonymous
 one year ago
Math help!

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ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1Do you know calculus? Or do you need to graph to solve?

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0I know calculus. I have to get the second derivative of this equation correct? And then set it equal to 0 and find the xvalues?

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1If x is an inflection point for y then the second derivative, y″(x), is equal to zero if it exists, but this condition does not provide a sufficient definition of a point of inflection. That's to say that if it y″(x) = 0, then it is not necessarily an inflection point. You are looking for the point where the function goes from concave up to concave down or vice versa. See red in this graph  https://en.wikipedia.org/wiki/Inflection_point#/media/File:Animated_illustration_of_inflection_point.gif

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1Here is a graph of your function. You can see where your function is concave up and concave down. Where it switches (from down to up or vice versa) is where you will test that in fact the second derivative is zero at that point and confirm that it is an inflection point.

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Wheres the graph of the function?

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1Where it goes from Concave down to Concave up is your inflection point

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1Now take the second derivative and set equal to zero. The point in that vicinity is the inflection point.

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1The second derivative set equal to zero is d^2/dx^2(x^3+18 x^23 x+4) = 6 (x+6) =0 So x = 6, right?

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1A little cleaner  $$ \frac{d^2}{dx^2}\left (x^3+18 x^23 x+4 \right )=6(x+6)=0 $$ This is your equation, right?

ybarrap
 one year ago
Best ResponseYou've already chosen the best response.1Here is the second derivative  http://www.wolframalpha.com/input/?i=d%5E2%2Fdx%5E2+%28x%5E3+%2B+18x%5E2+%E2%80%93+3x+%2B+4%29

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Okay yeah I messed up when deriving
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