`A=1/(\sqrt{3}+\sqrt{2})-(\sqrt{15}-\sqrt{12})/(\sqrt{5}-2)`
`=1/(\sqrt{3}+\sqrt{2})-(\sqrt{3}(\sqrt{5}-\sqrt{4}))/(\sqrt{5}-\sqrt{4})`
`=1/(\sqrt{3}+\sqrt{2})-\sqrt{3}`
`=(1-\sqrt{3}(\sqrt{3}+\sqrt{2}))/(\sqrt{3}+\sqrt{2})`
`=(1-3-\sqrt{2})/(\sqrt{3}+\sqrt{2})`
`=(-2-\sqrt{2})/(\sqrt{3}+\sqrt{2})`