I.
x²=7
x = ±√7 => x=√7 ; x=-√7
2x²=98
x² = 49
x=√49
x=7
x²+2=0
x²=-2
x = ±√2 (faci ca in primul ex.)
II.
69-5(x-2)²=24
69 - 5(x²-2*x*2+2²)=24
69 - 5(x²-4x+4)=24
69 - 5x²+20x-20=24
49-5x²+20x=24
-5x²+20x=24-49
-5x²+20x = 25
-5x²+20x-25=0 | :5
-x²+4x-5=0 / *(-1)
x²-4x-5=0
x² x+(-5x) -5=0
x(x+1) -5(x+1)=0
(x+1)(x-5)=0
x+1=0
x=-1
x-5=0
x=5
S:{-1;5}
