We must factor the denominators first. And to factor a quadratic equation, you need its roots.
We will use the fact that any quadratic equation with leading coefficient 1, i.e. in the form
has the following properties:
- The sum of the roots is
![-b](https://img.qammunity.org/2021/formulas/mathematics/middle-school/125sy0i98loazva6rxzn6869xem75tkqdz.png)
- The product of the roots is
![c](https://img.qammunity.org/2021/formulas/mathematics/middle-school/nmow8g9n0xesktfk3ydy9if1ymfizkamxv.png)
So, for the first denominator, we're looking at two numbers such that their sum is -4 and their product is -12. It's easy to find out that those numbers are 2 and -6.
Similarly, for the second denominator, we're looking at two numbers such that their sum is -7 and their product is 6. It's easy to find out that those numbers are -1 and -6.
So, you can rewrite the expression as follows:
![(x^2+6)/((x-2)(x+6))+(7x)/((x+1)(x+6))](https://img.qammunity.org/2021/formulas/mathematics/high-school/os8aggxr7wllt0jb1jrujw4jlfl0qdlc8a.png)
The least common denominator is formed by the factors of the two denominators, and you have to select repeating ones only once.