# Week 15 in prec 11

This week we learnt the chapter Rational Expressions and Equations.

For each expression:

1. Factor the numerator and denominator.

2. Identify the non-permissible values of the variables.

3. Divide the numerator and denominator by their common factors.

This is the normal steps in solving the expressions, like this example:

Frist, we should factor it into $\frac{9(2+x)(2-x)}{(x-2)(x-3)}$

and we can cancel the x-2, but here we should cancel into -1 because they and opposite number,

we will get $\frac{-9(2+x)}{(x-3)}$, but don’t forget the non-permissible, here the x can’t equal to 2 and 3, because we can’t divide by zero.