.已知函数f(x)=x2+|x-a|+1,a∈R. (1)试判断f(x)的奇偶性; (2)若-≤a≤,

.已知函数f(x)=x2+|x-a|+1,a∈R.

(1)试判断f(x)的奇偶性;

(2)若-≤a≤,求f(x)的最小值.

答案

(1)f(x) 为非奇非偶函数(2)a2+1


解析:

(1)当a=0时,函数f(-x)=(-x)2+|-x|+1=f(x),

此时,f(x)为偶函数.当a≠0时,f(a)=a2+1,f(-a)=a2+2|a|+1,

f(a)≠f(-a),f(a)≠-f(-a),此时,f(x) 为非奇非偶函数.

(2)当x≤a时,f(x)=x2-x+a+1=(x-)2+a+,

∵a≤,故函数f(x)在(-∞,a]上单调递减,

从而函数f(x)在(-∞,a]上的最小值为f(a)=a2+1.

当x≥a时,函数f(x)=x2+x-a+1=(x+)2-a+,

∵a≥-,故函数f(x)在[a,+∞)上单调递增,从而函数f(x)在[a,+∞)上的最小值为f(a)=a2+1.

综上得,当-≤a≤时,函数f(x)的最小值为a2+1.

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