f(x)=x^2+4x+3
對(duì)稱軸是x=-2
函數(shù)g(t)表示函數(shù)f(x)在區(qū)間[t,t+1]的最小值
下面分類討論:
(1)若t+1＜-2,即t＜-3
則g(t)=f(t+1)=(t+1)^2+4(t+1)+3=t^2+6t+8
(2)若t≤-2≤t+1,即-3≤t≤-2
則g(t)=f(-2)=(-2)^2+4*(-2)+3=-1
(3)若t＞-2
則g(t)=f(t)=t^2+4t+3
所以g(t)=t^2+6t+8 (t＜-3)
=-1 (-3≤t≤-2)
=t^2+4t+3 (t＞-2)
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