Răspuns:
5. a) [tex]x^{2}[/tex] -5x+6= 0 Δ = [tex]b^{2}[/tex]-4ac= 25-4*6=1
x1= (-b- [tex]\sqrt{D }[/tex])/2a= (5-1)/2= 4/2=2 x1=2
x2= (-b+[tex]\sqrt{D}[/tex])/2a= (5+1)/2= 6/2= 3 x2=3
b) [tex]x^{2}[/tex] +x- 6=0 Δ = 1+24= 25
x1= (-1-5)/2= -6/2= -3 x1= -3
x2=(-1+5)/2= 4/2= 2 x2=2
c) [tex]x^{2}[/tex]- 7x+12= 0 Δ = 49-48=1
x1=(7-1)/2= 6/2= 3 x1=3
x2=(7+1)/2=8/2=4 x2= 4
d) [tex]x^{2}[/tex] +x-12= 0 Δ = 1+48=49
x1=(-1-7)/2=-8/2= -4 x2= (-1+7)/2= 6/2= 3
6. a)2[tex]x^{2}[/tex] +x-3= 0 Δ = 1 +4*3*2=25
x1=(-1-5)/4= -6/4= -3/2
x2=(-1+5)/4=4/4=1
b) 2[tex]x^{2}[/tex] -x -15=0 Δ = 1+15*2*4=121
x1=(1-11)/4= -10/4= -5/2
x2=(1+11)/4= 12/4=3
c) 3[tex]x^{2}[/tex] -5x+2= 0 Δ = 25- 2*3*4= 1
x1=(5-1)/6= 4/6= 2/3
x2=(5+1)/6= 6/6=1
d) 2[tex]x^{2}[/tex] -5x+2 =0 Δ = 25- 2*2*4=9
x1=(5-3)/4=2/4= 1/2
x2=(5+3)/4=8/4=2
