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8x-x^2-21=0
We add all the numbers together, and all the variables
-1x^2+8x-21=0
a = -1; b = 8; c = -21;
Δ = b2-4ac
Δ = 82-4·(-1)·(-21)
Δ = -20
Delta is less than zero, so there is no solution for the equation
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