Respostas

A melhor resposta!
2014-04-24T22:44:35-03:00
Basta utilizar a equação de delta e Bhaskara para chegar a um resultado
Δ=b²-2.a.c
Δ=-2²-4.-1.15
Δ=4-(-60)
Δ=64
--------
x=-b+-√Δ /2a
x=-(-2)+-√64 /2.-1
x=2+-8/-2

x1=-5
x2=3

1 5 1
  • Usuário do Brainly
2014-04-24T23:23:28-03:00
-x²- 2x +15 = 0

sabendo que:  a = -1,  b = -2 ,  c = 15 então:
resolvendo o valor de delta temos:
                                                  Δ = b² - 4ac
                                                  Δ = -2² - 4(-1)(15)
                                                  Δ = 4 + 60
                                                  Δ = 64
como delta é igual a 64, logo sua raiz é 8.

encontrando o valor das raizes reias.
                                                     X = -b +- √Δ / 2a
                                                     X1 = -(-2) + 8/ 2(-1)
                                                     X1 = 2+8/-2
                                                     X1 = 10/-2 = -5

                                                     X2 = -(-2) - 8 /-2
                                                     X2 = 2-8/-2
                                                     X2 = -6/-2 = 3
 LOGO, AS RAIZES SÃO: S = { -5, 3 }.