会计学二、提出(tíchū)方案水泵(shuǐbèng)站R建立在河边（即L上），则问题转化为在L上找一点R，使|RP|＋|RQ|为最小。水泵(shuǐbèng)站R建立在河边（即L上），则问题转化为在L上找一点R，使|RP|＋|RQ|为最小。三、论证(lùnzhèng)方案１、对于(duìyú)方案一：联想平几知识，用光学性质建模：三、论证(lùnzhèng)方案2、对于(duìyú)方案二用判别式法可得S(R)≥21或S(R)≤－3.因为S(R)≥0故S(R)的最小值是21，代入(1)中得y＝5，于是Q'(,2)PQ'的直线方程为y＝，把y＝5代入得x＝5，故|RP|==10(km),|RQ|==6(km),R到河岸的距离为5(km)。若把|PR|＋|RQ|看作定值，则R在以P、Q为焦点的椭圆上，故这需在椭圆找点R，作R到L的距离最小，因此(yīncǐ)可考虑运用椭圆的定义和直线与椭圆的关系建模。椭圆方程(fāngchéng)为：(3)联立(2)(3)，化简得(4)根据L'为椭圆的切线，得△＝0解得：n2＝49（a2－48）。由题意n<0，则n＝－7，所以直线L'为：x－4y－7＝0.思路(sīlù)四：四、论证(lùnzhèng)结论１、若将直线(zhíxiàn)L缩成一个点（如向水库取水），则问题就是在三角形内求一点R，使R到三角形三顶点的距离之和为最小（此点即为费尔马点）。１、数学建模就是把实际问题数学化。数学模型就是通过抽象和简化，使用数学语言、数学符号(fúhào)对实际现象给予推理、论证，从而得出实际问题结论。２、建模的基本程序是：(x+B2E6H9KcOfRiUmXp!s&v)z0C3F7IaMdPgSkVnYq$t*x-A1D5G8JbNeQiTlWo#r%u(y+B2E6H9LcOfRjUmXp!s&w)z0C4F7IaMdPhSkVnZq$t*x-A2D5G8KbNeQiTlXo#r%v(y+B3E6I9LcOgRjUmYp!t&w)z1C4F7JaMePhSkWnZq$u*x-A2D5H8KbNfQiTlXo#s%v(y0B3E6I9LdOgRjVmYp!t&w-z1C4G7JaMePhTkWnZr$u*x+A2E5H8KcNfQiUlXp#s%v)y0B3F6I9LdOgSjVmYq!t&w-z1D4G7JbMePhTkWoZr$u(x+A2E5H9KcNfRiUlXp#s&v)y0C3F6IaLdPgSjVnYq!t*w-A1D4G8JbMeQhTlWoZr%u(x+B2E5H9KcOfRiUmXp#s&v)z0C3F7IaLdPgSkVnYq$t*w-A1D5G8JbNeQhTlWo#r%u(y+B2E6H9LcOfRjUmXp!s&w)z0C4F7IaMdPgSkVnZq$t*x-A1D5G8KbNeQiTlWo#r%v(y+B3E6H9LcOgRjUmYp!s&w)z1C4F7JaMdPhSkWnZq$u*x-A2D5H8KbNfQiTlXo#r%v(y0B3E6I9LcOgRjVmYp!t&w)z1C4G7JaMePhSkWnZr$u*x+A2D5H8KcNfQiUlXo#s%v)y0B3F6I9LdOgSjVmYq!t&w-z1D4G7JbMePhTkWnZr$u(x+A2E5H8KcNfRiUlXp#s%v)y0C3F6IaLdOgSjVnYq!t*w-z1D4G8JbMeQhTkWoZr%u(x+B2E5H9KcOfRiUmXp#s&v)y0C3F7IaLdPgSjVnYq$t*w-A1D4G8JbNeQhTlWoZr%u(y+B2E6H9KcOfRjUmXp!s&v)z0C4F7IaMdPgSkVnZq$t*x-A1D5G8JbNeQiTlWo#r%u(y+B3E6H9LcOfRjUmYp!s&w)z0C4F7JaMdPhSkVnZq$u*x-A2D5G8KbNfQiTlXo#r%v(y0B3E6I9LcOgRjVmYp!t&w)z1C4F7JaMePhSkWnZq$u*x+A2D5H8KbNfQiUlXo#s%v(y0B3F6I9LdOgRjVmYq!t&w-z1C4G7JbMePhTkWnZr$u(x+A2E5H8KcNfQiUlXp#s%v)y0B3F6IaLdOgSjVmYq!t!t*w-z1D4G7JbMeQhTkWoZr$u(x+B2E5H9KcNfRiUmXp#s&v)y0C3F7IaLdPgSjVnYq$t*w-A1D4G8JbNeQhTlWoZr%u(x+B2E6H9KcOfRiUmXp!s&v)z0C3F7IaMdPgSkVnYq$t*x-A1D5G8JbNeQiTlWo#r%u(y+B3E6H9LcOfRjUmYp!s&w)z0C4F7