In week 12 of precalc 11 we went over the basics of non-permissible values in fractions. Basically, if the value of the denominator (bottom of the fraction) is zero, then it doesn’t work. This is because you can’t divide anything by 0, like imagine taking groups of 0 out of something, it just doesn’t work.

Now the fractions we’ve been working with usually have an X value and an integer on the bottom. We have to find a way to make it 0 with our given numbers (We have to find out how to make it 0 so we can avoid making it 0).

Basically if we have X-5 on the bottom, X can NOT equal 5 because 5-5 is zero.

To make it more complicated we can have a coefficient on X, so we could have it be 2X-5 on the bottom. To make the bottom be zero we will have to first divide the 2x by two and so we must also divide -5 by 2, resulting in X-5/2 on the bottom. Then X will have to be NOT equal to 5/2, because 5/2-5/2=0

To make it even more complicated we can have binomials such as (2X-5) (X+7) on the bottom. To find a binomial’s non permissible values, you will have to solve both the brackets, the logic behind this is that the brackets multiply, so if just one of them equal 0, then it will multiply the other by 0, resulting in 0. Nonetheless you must still solve both brackets because either bracket could multiply the other or something like that. so it will be X≠5/2 and/or -7.

Long story short, if you can make the bottom of a fraction zero, the numbers you used will be known as non-permissible.