log2(4^x+4)=log2(2^x)+log2[2^(x+1)-3]令2^x=a4^x=a² 2^(x+1)=2alog2(a²+4)=log2(a)+log2(2a-3)log2(a²+4)=log2(2a²-3a)a²+4=2a²-3aa²-3a-4=0a=4,a=-1a=2^x>0所以2^x=4x=2