若x1满足2x+2x=5,x2满足2x+2log2(x-1)=5,则x1+x2=______

日期:2016-10-30 10:06:54 人气:1

若x1满足2x+2x=5,x2满足2x+2log2(x-1)=5,则x1+x2=______

由题意 2x1+2x1=5①2x2+2log2(x2-1)=5 ②所以由①得:2x1=5?2x1?x1=log2(5-2x1)即2x1=2log2(5-2x1)令2x1=7-2t,代入上式得7-2t=2log2(2t-2)=2+2log2(t-1)?5-2t=2log2(t-1)又∵由②式得:5-2x2=2log2(x2-1),易知t=x2于是2x1=7-2x2即x1+x2=72故答案为:72.
    A+
热门评论