let the polynomial on the LHS be f(x), (f(2)/f(1))<0,upon simplification, we get 4e^a -2e^2a +e^a -1>0
solving this quadratic inequality in e^a =y, we get (5-√17)/4<y<(5+√17)/4,therefore
ln((5-√17)/4)<a<ln((5+√17)/4)
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