x^2 - xy + y^2 = 1
x^2 - xy + y^2 - 1 = 0
y^2 -xy + x^2 -1 = 0
a = 1, b = -x, c = (x^2 - 1)
y = - (-x) + or - sqrt[(-x)^2 - 4*(x^2 - 1)]
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2
y = x + or - sqrt[x^2 - 4x^2 + 4]
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2
y = x (+ or -) sqrt(-3x^2 + 4)
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2