令f(x)=x^2+x由图像可知,f(x)在（负无穷大,-1/2）上递减,在[-1/2,正无穷大）递增,所以f(x)在[-1,-1/2)上递减,在[-1/2,3]上递增故当x=-1/2时有最小值,即y=(-1/2)^2-1/2=-1/4x=3时,y有最大值,即9+3=12故y=x的平方+x（-...