# How do you simplify #(5x+15)/(x^2+10x+21)# and then find the excluded values?

##### 1 Answer

Nov 8, 2017

#### Explanation:

Always. ALWAYS factorise an algebraic fraction (if you can). We can factorise the top to

This helps us out, we can be pretty sure the quadratic will have

In maths, dividing by zero does loads of crazy things, so we need to exclude the x that would make then denominator equal to zero.

let