GRE
$$\frac{w+z}{2}$$
$$x+\frac{z-y}{2}$$
$$(\frac{1}{x}-\frac{1}{y})^{-1}$$
$$(\frac{1}{y}-\frac{1}{z})^{-1}$$
The average (arithmetic mean) of the numbers x, -x, and |x|
x
25000 +道题目
247本备考书籍