Contract the expressions given in Problems 25-28. That is, use the properties of logarithms to write each expression as a single logarithm with a coefficient of 1.

a. \(\log \left(x^{2}-9ight)-\log (x+3)\)

b. \(\log \left(x^{2}-x-6ight)-\log (x+2)\)

c. \(\ln \left(x^{2}-4ight)-\ln (x+2)\)