设x+1=m,则x=m-1
x^2+x-6
=(m-1)^2+m-1-6
=m^2+1-2m+m-7
=m^2-m-6
=(m-1/2)^2-25/4
当m=1/2即x=-1/2时,f(x)有最小值-25/4
还有什么不懂请追问