f (x) is defined forx12−x9+x4−x+1>0 ⇒x4x8+1−xx8+1+1>0⇒x8+1xx3−1+1>0 If x≥1 or x≤−1, then the above expression is positive. If −10 ∵x4+1>x8+1 and so x4+1>xx8+1The domain of f=(−∞,∞)