==> \({x^2} + 13x + 15 = A{(x + 3)^2} + B(2x + 3)\,(x + 3) + C(2x + 3)\)
For \(x = - 3,\,C = 5\) and for \(x = - {3 \over 2};\,A = - 1\)
Equating coefficient of \({x^2}\)
\(1 = A + 2B \Rightarrow B = {{1 - A} \over 2} = 1\)
\(\therefore \) Given expression = \({1 \over {x + 3}} - {1 \over {2x + 3}} + {5 \over {{{(x + 3)}^2}}}\).