2) x^2-11x+30=0
D= 121-4*30*1=121-120=1
x1= (11+1):2=12/2=6
x2= (11-1):2=10/2=5
4) x^2-21x+110=0
D= 441 -4*110*1=441-440=1
x1= (21+1):2=22/2=11
x2= (21-1):2=20/2=10
2) 4x^2-64=0
(2x-8)(2x+8)=0
2x-8=0 или 2x+8=0
2x=8 2x=-8
x=4 x=-4
4)4x^2-2x-0,75=0
D= 4- 4*(-0,75)*4=4+12=16
x1= (2+4):2=6/2=3
x2= (2-4):2= -2/2=-1