2x^4-4x^2-1-(x^2-2x^2-4)=2x^4-x^2+3把x^2看成t,原式=2t^2-t+3f(t)=2t^2-t+3在[0,∞)上的最小值=f(1/4)=23/8>0f(t)=2t^2-t+3在[0,∞)上恒大于02x^4-x^2+3恒大于02x^4-4x^2-1恒大于x^2-2x^2-4...