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

日期:2016-12-02 04:27:34 人气:2

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

答: x1满足:2x+2^x=5,2x1+2^(x1)=5 x2满足:2x+2log2(x-1)=5,2x2+2log2(x2-1)=5 设t=log2(x2-1) 则x2-1=2^t 所以:x2=1+2^t 所以:2(1+2^t)+2t=5 所以:2(t+1)+2^(t+1)=5 所以: x1和t+1都是方程2x+2^x=5的解 所以:x1=t+1=log2(x2-1)+1=log2(2x2-2) 2x2-2=2^(x1) 2x2=2+2^(x1) 所以: 2x1+2x2=2
    A+
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