How do you do a sign chart?

Question

Our teacher showed us some way to solve problems. There was something that went along the top, and something down the sides and in the middle we decided wether the expression was possitive or negative. I just don't know how to set it up. <><

Answer 1

You need some critical points. If you are preparing this for the function "f", then it is the points where f is undefined or zero. In calculus most often f is the first or the second derivative of a function F for example. After you find these you put them on a horizontal line starting from the lowest and going right in order. Don't forget to leave some space between them and on the left and right before the first and after the last too. So if you have k critical points, then you have k+1 regions on the number line separated by those critical points. Now starting from the left most region, ask yourself this question: "Do I get a positive or a negative number if I plug in a number in this region into f?" For this, if you had found your critical points correctly, it is quite OK to just pick a number inside that region and plug into f. Now if you get a positive number you mark the region + otherwise - and move onto the next region. Depending on the type of function you are considering there are some nice shortcuts to this method but for the first few tries this much information should be enough for you.

Answer 2

this is nearly impossible over the internet with limited keys... basically it is a number line and u plug numbers into an equation and see if you get positive or negative numbers which allows you to determine to relative shape of the graph

Answer 3

you need the explain further...
what do you mean?