Respostas

  • Usuário do Brainly
2014-07-30T14:28:30-03:00
A)
x²-x-20=0
Δ=1+80
Δ=81
√Δ=√81=± 9

x'=  \frac{1+9}{2} = \frac{10}{2} =5

x"= \frac{1-9}{2} =- \frac{8}{2} =-4

S={-4,5}

b)
x²-3x-4=0
Δ=9+16
Δ=25
√Δ=√25=± 5

x'= \frac{3+5}{2} = \frac{8}{2} =4

x"= \frac{3-5}{2} =- \frac{2}{2} =-1

S={-1,4}

c)
x²-8x+7=0
Δ=64-28
Δ=36
√Δ=√36= ± 6

x'= \frac{8+6}{2} = \frac{14}{2} =7

x"= \frac{8-6}{2} = \frac{2}{2} =1

S={1,7}