O functie de gradul I este strict crescatoare daca: a>0.
In cazul de fata a=m²-4 si avem conditia:
m²-4>0
(m+2)(m-2)>0
Si facem tabel de semn:
__m__|-inf_________-2____________2______________inf
_m²-4_|++++++++++++++0----------------------0++++++++++++++++++
m²-4>0 => m∈(-inf;-2)∪(2;inf).