4X - Y = 9
3X^2 + Y = 11
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4X + 3X^2 - Y + Y = 9 + 11
3X^2 + 4X - 20 = 0
D = 16 + 240 = 256 ; √ D = 16
X1 = ( - 4 + 16 ) : 6 = 2
X2 = ( - 4 - 16 ) : 6 = - 10/3 = - 3 ( 1/3 )
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Y = 4X - 9
Y1 = 8 - 9 = - 1
Y2 = 4 * ( - 10/3 ) - 9 = - 40/3 - 27/3 = - 67/3 = - 22 ( 1/3 )
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