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问题: 高一数学题

已知二次函数f(x)=mx~2+(m-3)x+1,对于任意实数x,恒有f(x)小于等于f(m),(m为常数),且等号能够取到,求m的值.

解答:

二次函数f(x)=mx~2+(m-3)x+1,对于任意实数x,恒有f(x)小于等于f(m)
即 f(x)<=0 (m-3)^2-4*m*1<=0 (1)
f(m)>=0 m^3+m^2-3m+1>=0 (2)
解(1)得 m^2-6m+9-4m<=0
(m-9)(m-1)<=0
{m>=9 {m<=9
{m<=1舍弃 {m>=1

解(2)得 (m-1)(m^2+2m-1)>=0
{m>=1 {m<=1

{m>=√2-1 {m<=√2-1
{m>=-√2-1 {m<=-√2-1
综上 1<=M<=9