Question

Resolva os sistemas:
xy=21
x+y=10

Answer 1

Xy=21             y=21/x
x+y=10
x+21/x=10
X²+21=10x
X²-10x+21=0 

100-84

Δ= 16 

10+-√16/2
X'=10+4/2 = 14/2 = 7 
X''=10- 4/2 = 6/2 = 3 

X=7 Y= 3