MathRevolution
[GMAT math practice question]
\(<x, y>\) is defined as \(\frac{(2x+y)}{(x-2y)}.\) What is the value of \(<\frac{1}{2}, \frac{2}{3} >- <\frac{1}{3} , \frac{1}{4} >\)?
\(A. \frac{5}{2}\)
\(B. \frac{5}{3}\)
\(C. \frac{7}{2}\)
\(D. \frac{3}{2}\)
\(E. \frac{8}{3}\)
\(<x, y>\) is defined as \(\frac{(2x+y)}{(x-2y)}\)
\(<\frac{1}{2}, \frac{2}{3} > = \frac{2(\frac{1}{2})+\frac{2}{3}}{\frac{1}{2}-2(\frac{2}{3})}\) \(=\frac{(1)+(\frac{2}{3})}{(\frac{1}{2})-(\frac{4}{3})} = \frac{\frac{(3+2)}{3}}{\frac{(3-8)}{6}} = \frac{5}{1}*\frac{2}{(-5)} = -2\)
\(<\frac{1}{3}, \frac{1}{4} > = \frac{2(\frac{1}{3})+\frac{1}{4}}{\frac{1}{3}-2(\frac{1}{4})}\) \(=\frac{(\frac{2}{3})+(\frac{1}{4})}{(\frac{1}{3})-(\frac{1}{2})} = \frac{\frac{(8+3)}{12}}{\frac{(2-3)}{6}} = \frac{11}{2}*\frac{1}{(-1)} = -\frac{11}{2}\)
Hence,
\(<\frac{1}{2}, \frac{2}{3} >- <\frac{1}{3} , \frac{1}{4} > =\) \(-2-(\frac{11}{2})\) \(= -2+\frac{11}{2}= \frac{-4+11}{2} = \frac{7}{2}\)
Answer C...