Indefinite Integration

If \(\int \sqrt{\frac{x-7}{x-9}} d x=A \sqrt{x^2-16 x+63}+\log \left|(x-8)+\sqrt{x^2-16 x+63}\right|+c,\)

(where \(\mathrm{c}\) is a constant of integration) then \(\mathrm{A}\) is