19+99n+n²=0两边除以n²得
19/n²+99/n+1=0
与19m^2+99m+1=0比较得
m,1/n是方程19x²+99x+1=0的两个根
于是
m+1/n=-99/19
m/n=1/19
(mn+4m+1)/n
=m+1/n+4m/n
=-99/19+4/19
=-5
19+99n+n²=0两边除以n²得
19/n²+99/n+1=0
与19m^2+99m+1=0比较得
m,1/n是方程19x²+99x+1=0的两个根
于是
m+1/n=-99/19
m/n=1/19
(mn+4m+1)/n
=m+1/n+4m/n
=-99/19+4/19
=-5