Axial symmetry

, ∴f(x) is

Even function

, as evidenced by the following:

F(x)

Domain of definition

For r,

For any x in the domain,

f(-x)= 1-|-x | = 1-| x | = f(x)，

Then f(x) is an even function;

(3)f(x)

Zen increase

The interval is (-∞, 0),

When x=0, the maximum value of f(x) is1;

④ Let f(x)=0, then |x|= 1, x = 1,

Then the zero point of f(x) is x =1;

X that makes f (x) > 0.

Value range

Is {x |- 1 < x < 1}.