Question

x+y=5,x²+y²=20

Answer 1

x+y=5,x²+y²=20

2xy = (x+y)² - (x²+y²) = 25 - 20 = 5

(x-y)² = (x²+y²) - 2xy = 20 - 5 = 15

x-y = ± 根号15

2x = ( x+y ) +( x-y ) = 5 ± 根号15

x = 2分之 ( 5 ± 根号15)

y = 2分之 ( 10 -5 ± 根号15)

= 2分之 ( 5 -+ 根号15)