Respostas

2013-09-26T16:25:11-03:00
y= -x²+5
     -x² = - 5 .(-1)
      x² = 5
      x = 
± √5

y=-x²+x+2

a = -1
b = 1
c = 2

Δ = b² - 4 ac
Δ = 1² - 4 . (-1) . 2
Δ = 1 + 8
Δ = 9

x= -b ± √Δ / 2a
x= -1 ± √9 / 2.(-1)
x= -1 ± 3 / -2

x' = -1 +3 / -2 = 2/-2 = -1
x'' = -1 -3 / -2 = -4/-2 = 2 
1 5 1