設函數(shù)f(x)=|2-x^2|,若0<m<n,且f(m)=f(n),則mn范圍是
設函數(shù)f(x)=|2-x^2|,若0<m<n,且f(m)=f(n),則mn范圍是
數(shù)學人氣:114 ℃時間:2020-03-22 21:47:57
優(yōu)質解答
f(m)^2-f(n)^2=0
(2-m^2)^2-(2-n^20^2=0
m^4-4*m^2-n^4+4*n^2=0
(m^2+n^2)*(m^2-n^2)-4*(m^2-n^2)=0
(m^2+n^2-4)*(m+n)(m-n)=0
因為0所以m^2+n^2=4
(m-n)^2=m^2-2mn+n^2>0
4-2mn>0
mn<2
因m>0,n>0
故0