x^2-mx+10=0, m∈R
x2-x1=3 => x2=3+x1;
x1,x2 solutile ecuatiei =>
(3+x1)^2-m(3+x1)+10=0;
9+6x1+x1^2-3m-mx1+10=0;
x1^2-x1*(m-6)+19-3m=0;
Δ=(m-6)^2+12m-46;
Δ=m^2-12m+12m+36-76
Stind ca ecuatia are 2 solutii reale diferite, Δ>0=>
Δ=m^2-40>0 => |m|>2√10=> m∈(-∞,2√10)∪(2√10,+∞);