lean_workbook_plus_19477

Rewrite as: $a^4-a^3-a+1 \ge 0$ Yeah. $3(a^4+a^2+1) \ge (a^2+a+1)^2$ $\iff a^4-a^3-a+1 \ge 0$ $\iff (a-1)^{2}( a^2 +a +1) \ge 0$ $\Leftarrow a^2 +a +1=(a+\frac{1}{2})^2+\frac{3}{4}> 0$