請寫過程式。謝謝
熱心網(wǎng)友
解:f(x)=0,三根是x1＜x2＜x3①a＞0∵當(dāng)x＞x3時,f(x)a(x-x1)(x-x2)(x-x3)＞0說明a＞0.②b＜0∵f(x)=a(x-x1)(x-x2)(x-x3)=ax^3-a(x1+x2+x3)x^2+......b=-a(x1+x2+x3)∵a＞0,x1+x2+x3＞0[注:若x1=0,x2=1,x3=2,顯然x1+x2+x3=3＞0]∴b＜0
請寫過程式。謝謝
解:f(x)=0,三根是x1＜x2＜x3①a＞0∵當(dāng)x＞x3時,f(x)a(x-x1)(x-x2)(x-x3)＞0說明a＞0.②b＜0∵f(x)=a(x-x1)(x-x2)(x-x3)=ax^3-a(x1+x2+x3)x^2+......b=-a(x1+x2+x3)∵a＞0,x1+x2+x3＞0[注:若x1=0,x2=1,x3=2,顯然x1+x2+x3=3＞0]∴b＜0