(1) f(x)的定义域为R
f(-x)=(-x)²-4|-x|+3=(x)²-4|x|+3=f(x) f(x)为偶函数
(2)
(3)f(x)的单调增区间为(-2,0)和(2,+无穷)
单调减区间为(-无穷,-2)和(0,2)