∵不等式f[log2(x2+5x+4)]≥0．且f（2）=0，∴f(log2(x2+5x+4))≥f(2)．∵偶函数f（x）在（0，+∞）上为增函数，∴|log2(x2+5x+4)|≥2，∴log2(x2+5x+4)≥2或log2(x2+5x+4)≤−2．∴x2+5x+4≥22或0＜x2+5x+4≤2-2，...