Explicație pas cu pas:
a²+9a>=6a => a²+9a-6a>=0 => (a-3)²>=0 Adevarat
a⁴+100>=20a² => a⁴+100-20a²>=0 => (a-10)²>=0 Adevarat
a²+1/a²>=2 => a²+1/a²-2>=0 => (a-1/a)²>=0 Adevarat
a⁴+3a²+1>=2a³+2a =>
a⁴+3a²+1-2a³-2a>=0 =>
a⁴-2a³+a²+a²-2a+1+a²>=0=>
(a²-a)²+(a-1)²+a²>=0 Adevarat deaorece (a²-a)²>=0
(a-1)²>=0 , a²>=0
