(x+3)²=(x-1) (x+5)
x²+6x+9=x²+4x-5
2x=-14
x=-7
verificare ' -8;-4;-2 progresie geometrica cu ratia 2
8≥2x
x≤4 x∈(-∞;4]
3x²-x=0
x(3x-1)=0 xi=0; x2=1/3
2x²=-8
x²=-4, x1,2∉R adica in R, S=∅
-x²+4x+5=0
x²-4x-5=0 x1=5, x2=-1 pt ca x1+x2=4 si x1 *x2=-5
x²=2
x1=+√2; x2=-√2