If the point P (C, 2C) is in the ellipse x ^ 2 / A ^ 2 + y ^ 2 / b ^ 2 = 1 (a > b > 0), then the eccentricity of the ellipse E= Such as the title

If the point P (C, 2C) is in the ellipse x ^ 2 / A ^ 2 + y ^ 2 / b ^ 2 = 1 (a > b > 0), then the eccentricity of the ellipse E= Such as the title

c^2/a^2+4c^2/(a^2-c^2)=1,
e=c/a,
e^2+4e^2/(1-e^2)=1,
Let t = e ^ 2,
t+4t/(1-t)=1,
t^2-6t+1=0,
T = 3 ± 2 √ 2, ∵ 3 + 2 √ 2 ″ 1, should be omitted,
t=3-2√2,
e=√（3-2√2）=√（2-2√2+1）=√（√2-1）^2=√2-1.

Elden Ring Premiere

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