f(X)=X^2-4X-4=(X-2)^2-8当a+1<=2,即a<=1时,f(x)在[a,a+1]上单调减少,最小值f(a+1)=(a-1)^2-8=1==> (a-1)^2=9 ==> a-1=±3 ==> a=4(舍去) or a=-2 ==>a=-2当a>=2时,f(x)在[a,a+1]上单调增加,最小值f(a)=(a-2)^2-8=1==> (a-2)^2=9 ==> a-2=±3 ==> a=-1(舍去) or a=5 ==>a=5所以a=-2或a=5。