We have: frac(a^(2) - a - 2)(a^(2) - 13 a + 30)a2−a−2a2−13a+30
Let's factorise both the numerator and the denominator using the "middle-term break":
= frac(a^(2) + a - 2 a - 2)(a^(2) - 3 a - 10 a + 30)=a2+a−2a−2a2−3a−10a+30
= frac(a(a + 1) - 2(a + 1))(a(a - 3) - 10(a - 3))=a(a+1)−2(a+1)a(a−3)−10(a−3)
= frac((a + 1)(a - 2))((a - 3)(a - 10))=(a+1)(a−2)(a−3)(a−10)
Now let's evaluate the restricted values of aa.
The denominator of the fraction can never be equal to zero:
Rightarrow (a - 3)(a - 10) ne 0⇒(a−3)(a−10)≠0
Using the null factor law:
Rightarrow a - 3 ne 0, a - 10 ne 0⇒a−3≠0,a−10≠0
Rightarrow a ne 3, a ne 10⇒a≠3,a≠10
therefore frac(a^(2) - a - 2)(a^(2) - 13 a + 30) = frac((a + 1)(a - 2))((a - 3)(a - 10)); a ne 3, 10