在初中阶段所涉及的三种函数一次函数(包括正比例函数),二次函数,反比例函数中,只有反比例函数y=k/x(k≠0),对自变量x有要求,即x≠0.因为k≠0,则也必定y≠0,所以反比例函数的图象双曲线永远不会与坐标轴相交,因此它的性质中就特别强调:“在图象所在的每个象限内”这一条件.,若忽略这个条件,就会给后面的解题带来麻烦,这也从某个方面说明教材编写具有相当的严密性. Only the inverse function y = k / x (k ≠ 0) of the three functions involved in the junior middle school (including the proportional function), the quadratic function, and the inverse function requires the independent variable x, that is, x ≠ 0 Since k ≠ 0, then it must be y ≠ 0, so the image hyperbola of the inverse function never crosses the coordinate axis, so its characterization is particularly emphasized: “in each quadrant where the image is ”If you neglect this condition, it will cause problems for the following problem solving, which also shows that the compilation of textbooks is quite rigorous.