a. [tex]\int \frac{1}{6-x^2} = \int \frac{1}{12}(\frac{1}{6+x}+\frac{1}{6-x}) =\frac{1}{12}(ln(6+x)-ln(6-x))
b \int\frac{1}{2x^2+3x+5} = \int\frac{1}{(\sqrt{2}x+\frac{3}{2\sqrt{2}})^2+\frac{31}{8}} =\int\frac{1}{(\frac{\sqrt{31}}{2}x+\frac{3\sqrt{31}}{8})^2+1}.\frac{31}{8}=arctan(\frac{\sqrt{31}}{8}x+\frac{3\sqrt{31}}{8}).\sqrt{31}[/tex]