x ·( x + 1 ) = 600
x² + x = 600
x² + x - 600 = 0
x_{12} = \frac{-1+/- \sqrt{1+2400} }{2}= \frac{-1+/- \sqrt{2401} }{2}= \\ =\frac{-1+/-50}{2}
x = ( - 1 - 49 ) / 2 = - 50 : 2 = - 25
x = - 25, x + 1 = - 24
( - 25 ) · ( - 24 ) = 600
Answer:
C ) - 25
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