题目

Super- short tales of the unexpected, plus read- along tapes! Twenty soft- cover 16-page mini books help students attain reading success through a high interest approach (方法). Audio cassettes, perfect for the ESL (English as a second Language) students, build listening skills by teaching pronunciation, giving oral directions, and presenting vocabulary words in context. Each story is followed by four pages of short, simple comprehension and vocabulary exercises. Price: $6.00 for each pack of books (including five books). $7.00 for each cassettes (all together four cassettes). Publisher: Sh2．已知实数x，y满足x＞y＞0且x+y=1，则$\frac{2}{x+3y}+\frac{1}{x-y}$的最小值是$\frac{{3+2\sqrt{2}}}{2}$．