灵活地应用定比分点坐标公式。能使某些问题的求解简捷、明快. 一求量值例1 若a>o,b>0,且1/a+9/b=1,则a+b的最小值为——. 分析:由1/a+9/b=1易知直线l:x/a+y/b=1,过定点C(1,9),其中a,b分别为直线l在x轴与y轴正向上的截距.于是问题转化为:求过定点C(1,9)的直线的截距a,b之和的最小值.如图1.由定比分点坐标公式(C是 Apply flexibly the point-to-point coordinate formula. Can make the solution of some problems simple and clear. A solution to the value of 1 If a> o, b> 0, and 1 / a + 9 / b = 1, then the minimum value of a + b is -. Analysis: From 1/a+9/b=1, it is easy to know the straight line l:x/a+y/b=1, over the fixed point C(1,9), where a and b are respectively the straight line l on the x-axis and the y-axis. The problem is then transformed into: Find the minimum of the sum of the intercepts a, b and the intercept of the straight line over the fixed point C(1,9). As shown in Figure 1.