A= _____B= ______i need the answer for the missing blank

We have
[tex]f(x)=\frac{x^2-4x+3}{x^2+ax+b}[/tex]We have an asymptote in x=-4 and a discontinuity in x=3. Therefore, the denominator of the function is
[tex](x+4)(x-3)[/tex]we can expand the expression and obtain the next one
[tex]\begin{gathered} (x+4)(x-3)=x^2-3x+4x-12 \\ =x^2+x-12 \end{gathered}[/tex]The function is:
[tex]f\mleft(x\mright)=\frac{x^{2}-4x+3}{x^{2}+x-12}[/tex]So the coefficients on the denominator are:
a= 1
b= -12