log1/2 (4的x次方+2的x+1次方) = log1/2 (4的x次方）× log1/2 （2的x+1次方) = log1/2 (1/2)^-2x）+ log1/2 （ 1/2)^-(x+1) =-2x×[-(x+1)] =2x(x+1)＞0. 所以得x>0或x<-1.