289×5≈ ____
(Ⅰ)证明:f(x)在区间﹣1,1上是单调减函数;
(Ⅱ)解不等式f(x+ 12 )<f( 1x−1 );
(Ⅲ)若f(x)≤t2﹣mt﹣1对所有x∈﹣1,1,m∈0,1恒成立,求实数t的取值范围.
x-0.2=3.9 x=____