# Week 12 – Precalculus 11

Radical expressions are expressions that have a fraction and a variable in them. And something new that comes in with radical expressions are non-permissable values, which are values that make sure the variable if there is one on the denominator does not make 0, because you can’t divide by zero. an example of a radical expression with a variable on the denominator would be $\frac {2(x+2)}{x-4} \cdot \frac {x^2}{2-x}$. Since you have to simplify expressions by collecting like terms you need to know that if an there is a term like (x+2) on the denominator and there is a 2 on the numerator you can’t take the 2 out of the term since there is a plus sign beside the x. It would be also during this step that we would do the nonpermissable values since we aren’t dividing, with the non-permissable values being $x \neq 2,4$ from here we can safely simplify by multiplying through.