Question

Resolva os sistemas : x+y=9 xy=-10

Answer 1

x+y=9   ==>x=9-y  (i)

xy=-10  ==>x=-10/y (ii)

(ii) em (i)

-10/y=9-y

multiplique tudo por y

-10=9y-y²

y²-9y-10=0

y'=[9+√(81+40)]/2= (9+11)/2=10
y''=[9-√(81+40)]/2= (9-11)/2=-1

Se y=-1  ==>x=9-y=9+1=10 
Se y=10 ==>x=9 -10 =-1

Resposta {(10,-1) ; (-1,10)}