题目内容：

f(x)在x=0左右极限存在,下列不正确的 a.x->0+ limf(x) = x->0- limf(-x) b.x->0 limf(x*x)=x->0+limf(x
c.x->0 limf(|x|) = x->0+ limf(x) d.x->0 limf(x) = x->0+ limf(x);
有谁知道用什么原理推出来的,用分段函数举例出来的.
x->0+ limf(x) = x->0- limf(-x)
x->0 limf(x*x)=x->0+limf(x
c.x->0 limf(|x|) = x->0+ limf(x)
x->0 limf(x) = x->0+ limf(x);
根据已知条天怎么退出来的，根据极限定义x00- limf(-x)