The question says find apex, low point and the monotonic properties of the functions. a) b) c)...(adsbygoogle = window.adsbygoogle || []).push({});

To find intervals, I use the abc-formula. Example:

f(x) = 3x^3 - 3x

d/dx * f(x) = 3 * 3x^2 - 3, here a=3*3, b= -3 and c=0 (because there is none)

x1 = ( -b + sqrt(b^2 + 4*ac) ) / 2a

x2 = ( -b - sqrt(b^2 + 4*ac) ) / 2a

So from this I get 3 intervals:

[-infinity, x1], [x1, x2], [x2, +infinity]. Out of these intervals I can find out where graph rises and falls, in a 2 degree function.

In a 3 degree function there should be 4 intervals, correct? What would be the best approach to find all of them? I'm sorry if it's a stupid question, but I'm really struggling with this...

In the .pdf file you can see how I find the intervals (written as intervaller) and if the graph rises or lowers (written as stigning). Avoid the text as it's written in Norwegian.

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# B Finding intervals of a 3 degree function?

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