典例解析例1设xw R,求证:f(x)=(x2+2x+3)X2+(x2+2x+3)x4s>6.2证:令t=x+1,则g(t)=f (x) =(t2+2)(t」)+(t2+2)t42.分两种情形:(1)t(t2+2)(t」)2之29>6;(2)t>—2时,t+2>0.二g(t)至2t2j++2t七>21^t+2tH2=2t+2t+2t十2t十...