Explicație pas cu pas:
a) x²+10x+21=0 => delta = 100-84 =16
x1=-10+4/2=-6/2=-3
x2=-10-4/2=-14/2=-7
b) -x²+3x-2=0=> delta = 9-8=1
x1= -3+1/2=-2/2=-1
x2=-3-1/2=-4/2=-2
c) 6x²-5x+1=0 => delta = 25-24=1
x1=5+1/12=6/12=1/2
x2=5-1/12=4/12=1/3
d) x²-16x+64=0 => delta = 256 - 256=0 => x1=x2= -b/2a= 16/2=8
e) 2x²+x-1=0 => delta = 1+8=9
x1= -1+9/4=8/4=2
x2=-1-9/4=-10/4=-5/2
f) 3x²+6x+3=0 => delta = 36- 36=0=> x1=x2= -b/2a= -6/6=-1
