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Mathematics 15 Online
OpenStudy (anonymous):

Calculus Help

OpenStudy (anonymous):

OpenStudy (danjs):

they give you the first derivative of g. g ' (x) maybe start off by figuring out the function g(x) and thsecond derivative g ''(x)

OpenStudy (rizags):

The key critical values of a function g(x) occur where g'(x)=0 (Stationary Points), or g'(x) is undefined.

OpenStudy (anonymous):

I'm not sure how to "un-derive" but the second derivative I got was f''(x)=\[x^2-4x+16\]

OpenStudy (danjs):

well just g '' don't think you need g

OpenStudy (anonymous):

oops i forgot the denominator. x^2-4x+16/(x-2)^2

OpenStudy (anonymous):

for number 1, I set the first derivative to 0 and DNE. and I got -4,2,4

OpenStudy (rizags):

those should be your critical values. Concave up/down is determined by the sign of g''(x) at the key point. Simply evaluate g''(-4), g''(2), g''(4). If g''(x)>0, the graph is concave up there. If g''(x)<0, the graph is concave down there.

OpenStudy (rizags):

nevermind, sorry didn't read the question, you don't need that

OpenStudy (anonymous):

I thought I had to set the second derivative to 0 and DNE to find the inflection points. And those determine concave up or down? Thats number 3

OpenStudy (danjs):

|dw:1449622493694:dw|

OpenStudy (rizags):

g''(x)=0 and g''(x) DNE gives inflection points, yes. If g''(x)<0 for values in the interval between inflection points, then the graph of g is concave DOWN for that interval. Similarly, id g''(x)>0 for values in the interval between inflection points, the the graph of g is concave UP on that interval.

OpenStudy (danjs):

pick a value inside each interval, test it in g '(x), to see if you get + or -, inc or dec

OpenStudy (anonymous):

I had a problem setting the second derivative = to 0 and DNE. I couldn't get any points

OpenStudy (anonymous):

@DanJS I got decreasing, increasing, decreasing, decreasing

OpenStudy (danjs):

ok, the points are the critical points for #1 #2, say that for each interval (-inf,-4), (-4,-2)...

OpenStudy (danjs):

wait, x=5 gives + number, that is increasing

OpenStudy (anonymous):

I made the chart |dw:1449622831451:dw| youre right about the last one

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