Question

1.写出求二次函数y=ax^2+bx+c(a不为零）最值的算法

Answer 1

1

a>0 最小值 x=-b/2a y=c

a<0 最大值 x=-b/2a y=c

2

1/x+9/y=1

x=1/(1-9/y)=y/(y-9)

x+y=y/(y-9)+y=(y^2-9y+y)/(y-9)=(y^2-8y)/(y-9)