Question

resolva o sistema de equações:

(x-1)y=4
x+y=5

Answer 1

{(x-1)y=4
x+y=5

{xy-y=4
x+y=5

x=5-y. xy-y=4
(5-y)y-y=4
5y-y^2=4
-y^2+5y-4=0 (-1)
y^2-5y+4=0
a=1 b= -5 c=4
x= -b^2+-RAIZ QUADRADA b^2-4ac/2a
x= -(-5)+-RAIZ QUADRADA (-5)^2-4.1.4/2.1
x=5+-RAIZ QUADRADA 25-16/2
x=5+-RAIZ QUADRADA 9/2
x=5+-3/2
x1=5+3/2
x1=8/2
x1=4

x2=5-3/2
x2=2/2
x2=1