（1）x≥0时,f(x)=3x-x^3,f'(x)=3-3x^2=3(1-x^2)当0≤x≤1时,f'(x)≥0,函数单调递增；当x≥1时,f'(x)≤0,函数单调递减；∴此时,函数在x=1处取得极大值f(1)=3-1=2x≤0时,f(x)=3x+x^3,f'(x)=3+3x^2=3(1+x^2)>3∴此时函...