设f(x)=2(log2x)^ 2+2alog2 1/x+b,已知x=1/2时f(x)有最小值-8
(1)求a、b的值(2)求f(x)大于0的解集A(3)设集合B=(t-2分之1,t+2分之1),且A并B=空集,求实数t的取值范围
人气:142 ℃ 时间:2020-06-05 21:00:57
解答
(1)f(x)=2(log2x)^ 2+2alog2 1/x+b=2(log2x)^ 2-2alog2 x+b=2(log2 x-a/2)^ 2-a^2/2+b,得a=-2,b--6;
(2)解2(log2 x+1)^ 2-8>0即可(2,+∞)∪(0,1/8);
(3)分别解1/8=
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