Respostas

2014-07-23T15:51:38-03:00
X + y = -4, x . y= -21
X= 3 Y= -7
  • Usuário do Brainly
2014-07-23T16:25:24-03:00
 \left \{ {{x+y=-4} \atop {xy=-21}} \right.

isola
x=-4-y

subbst/
xy=-21

y(-4-y)=-21
-4y-y²+21=0
-y²-4y+21=0
y²=4y-21=0
Δ=16+84
Δ=100
√Δ=√100=10

y'= \frac{-4+10}{2} = \frac{6}{2} =3

y"= \frac{-4-10}{2} = \frac{-14}{2} =-7

como x=-4-y                          x=-4-y
  x=-4-3                                  x"=-4+7
x'=-7                                      x"=3

R= Os n° são -7 e 3