mai sus este o ecuatie de greadul doi. Calculezi delta dupa formula b^2-4ac ... in cazul tau Δ=16-4·(-5)=16+20=36
apoi calculezi radacinile x1 si x2 dupa formula x1,2= [(-b)plus minus √Δ]/2a
in cazul tau x1,2=[-4plus/minus 6]/2 rezulta x1=-4+6/2=1 si x2=-4-6/2=-5