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You do not need the quadratic formula, since this can easily be factored in to linear factors.

x2 + x - 20 = (x - 4)(x + 5), thus, x = 4 or 5.

But, using the quadratic formula:

(-b +- sqrt(b2 - 4ac))/2a = (-1 +- sqrt(1 + 80))/2

(-1 + 9)/2 = 4

(-1 - 9)/2 = -5

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15y ago

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