Х = 17 - Y
Y*( 17 - Y) - 9Y - 9*( 17 - Y) + 81 = 0
17Y - Y^2 - 9Y - 153 + 9Y + 81 = 0
- Y^2 + 17Y - 72 = 0
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D = 289 - 288 = 1 ; V D = 1
Y1 = ( - 17 + 1 ) : ( - 2 ) = + 8
Y2 = ( - 18 ) : ( - 2 ) = + 9
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X = 17 - Y
X1 = 17 - 8 = 9
X2 = 17 - 9 = 8