若0若0
若0X(5-2X)=-2(X-5/4)(X-5/4)-5/8当0<X<5/2时,当X=5/4时取得最大值,最大值为-5/8
f(x)=x(5-2x) =5x-2x^2 =-2(x-5/4)^2+25/8则函数在x=5/4处取得最大值则在(0,5/2),5/2>5/4fmax=f(5/4)=25/8