Question

resolva as equacoes de 2 grau usando formula geral a)-x2+x+12=0. B)7X2+X+1=0 C) X2-X-1=0

Answer 1

Delta: b²-4ac

Bháskara: - b ± √∆
––––––÷
2a


A) -x²+x+12=0

a=(-1), b= 1, c= 12

∆=b²-4ac
∆= 1²-4.(-1).(12)
∆= 1 + 48
∆= 49


bháskara:

x¹= -1 + 7 6
––––– = ––– ÷ = -3
-2 -2

x²= -1 - 7 -8
––––– = ––– ÷ = 4
-2 -2

S= {-3, 4}


B) 7x²+x+1=0

a= 7, b= 1, c= 1

∆=(-1)²-4. 7. 1
∆= 1 - 28
∆= -27 < {para aqui, pois raiz de delta negativo}


C) -x²-x-1=0

a=1, b= (-1), c= (-1)

∆=-(-1)²-4. 1. (-1)
∆=-1 + 4
∆= 3

bháskara:

x¹= - (-1) + 3 4
————— = ––– ÷ = 2
2 2

x²= - (-1) - 3 - 2
–––––– = –––– ÷ = - 1
2 2


S={2, -1}