We are give with the function:
[tex]{\quad \qquad \longrightarrow f(x)=\dfrac{x^{2}+x-12}{-4x^{2}-4x+8}}[/tex]
Vertical asymptotes are the points, where the function is not defined, so the denominator must be equal to 0 for making f(x) not defined
[tex]{:\implies \quad \sf -4x^{2}-4x+8=0}[/tex]
Dividing both sides by -4, we have;
[tex]{:\implies \quad \sf x^{2}+x-2=0}[/tex]
Can be further written as:
[tex]{:\implies \quad \sf x^{2}-x+2x-2=0}[/tex]
[tex]{:\implies \quad \sf x(x-1)+2(x-1)=0}[/tex]
[tex]{:\implies \quad \sf (x-1)(x+2)=0}[/tex]
Using zero product rule, Equating both multiplicants to 0, we have:
[tex]{:\implies \quad \boxed{\bf{x=1\quad or\quad -2}}}[/tex]
This is the required answer