解:因式分解得P=(log2(x)+t-1)(log2(x)-1)所以当log2(x)=1或1-t时,P=0当log2(x)>1且log2(x)>1-t时,P>0,此时x>2,t>1-1og2(x)>-2,log2(x)<3,x<8所以2
