2x - y = 5 ==> y = 2x - 5
X^2 - 2x( 2x - 5 ) + ( 2x - 5 )^2 = 9
X^2 - 4x^2 + 10x + 4x^2 - 20x + 25 = 9
X^2 - 10x + 16 = 0
D = 100 - 64 = 36 = 6^2
X1 = ( 10 + 6 ) : 2 = 8
X2 = ( 10 - 6 ) : 2 = 2
y1 = 2•8 - 5 = 11
y2 = 2•2 - 5 = - 1
Ответ ( 8 ; 11 ) ; ( 2 ; - 1 )