a) scoate x in afara parantezei
x(5x+0,2)=0
astfel
x=0 sau 5x+0,2=0
5x=-0,2
x=-0,2/5=-0,04
răspuns
x₁=0
x₂=-0,04
b) 5x²-6x+1=0
calculam Δ=b²-4ac=36-4*5*1=16
x1=(-b-√Δ)/2a=6-4/10=0,2
x2=(-b+√Δ)/2a=6+4/10=1
c) deschidem parantezele, trecem toti termenii intr-o parte
9x²-6x+7-6=0
9x²-6x+1=0
facem dupa formula ca in cazul b
calculam Δ=b²-4ac=36-4*9*1=36-36=0
x1=x2=(-b)/2a=6/18=1/3
