7X^2 - 54X + 35 = 0
D = 2916 - 980 = 1936 ; √ D = 44
X1 = ( 54 + 44 ) : 14 = 7
X2 = ( 54 - 44 ) : 14 = 2/7
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- 3X^2 - 28X - 49 = 0
D = 784 - 588 = 196 ; √ D = 14
X1 = ( 28 + 14 ) : ( - 6 ) = ( - 7 )
X2 = ( 28 - 14 ) : ( - 6) = ( - 7/3 ) = ( - 2 1/3 )
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- 3X^2 + 19X - 28 = 0
D = 361 - 336 = 25 ; √ D = 5
X1 = ( - 19 + 5 ) : ( - 6 ) = 7/3 = 2 1/3
X2 = ( - 19 - 5 ) : ( - 6 ) = 4