∵f(x) is increasing monotonously in the world.

∴2a≤ 1

∴a≤ 1/2

(2) Let x 1∑(0, +∞), then -x∑(-∞, 0).

∴f(-x)=x？ [Add to nouns in French etymology ending in -u to form plural]

The function f(x) is an even function on R.

∴f(x)=f(-x)=x？ The domain of -x is (0, +∞)

∴f(x)=x？ +x，x≤0

x？ -x，x≥0

Hope to adopt ~~=v=