What is the excluded value for the function posted in the comments? If you could also tell me how you know this, that would be very helpful...

Question

anonymous · Answer

$$y= \frac{ 3 }{ x+4 }$$

phi · Answer

There is an important "rule"  :  you are not allowed to divide by 0
dividing by 0 gives an undefined answer.

in your problem, if x is a certain number,  then x+4  becomes 0
you will want to "exclude that x value"

phi · Answer

can you figure out what x value makes    x+4= 0 ?

anonymous · Answer

-4

phi · Answer

so x= -4 is the excluded value

people write  x ≠ -4
to show x is not allowed to be -4 (otherwise you end up dividing by 0, and that is bad)

anonymous · Answer

thank you!