f(x)是定义在(-∞,0)上偶函数 偶函数 => f(x) = f(-x)只定义在(-∞,0) I suppose f(x) is even on Rx 0 ∈ (0,∞) f(-x) = (-x)^2 + (-x) + 4/(-x) = x^2 -x -4/x = f(x)f(x) = x^2+x+4/x for x > 0= x^2 -x -4/x fo...