Explicație pas cu pas:
1) x²-5x+6=0 => delta = 25-24=1 , x1= 5+1/2=6/2=3
x2= 5-1/2=4/2=2
2) x²-2x-3=0 => delta = 4+14=16 , x1= 2+4/2=3
x2=2-4/2=-1
3) x²-9=0 => x²=9 => x1= 3 , x2=-3
4) x²+4=0 => x²=-4 => ecuatia nu are soluții reale
5) x²-6x+9=0 => delta = 36-36 =0 => x1=x2 = -b/2a => x= 6/2=3
6) 2x²-5x+2=0 => delta = 25 - 16 = 9 => x1= 5+3/4=8/4=2 , x2= 5-3/4=2/4=1/2
