■平方根と連分数(その72)
λ>3のペル数を扱いたいのであるが、ax^2-bx-c=0
λ=√(9・a^2+4)/a
解の大きいほうが3より大きくなければならない。
{-b+√(9・a^2+4)}/2a>3
-b>6a-√(9・a^2+4)
|b|は3aよりおおくならなければならない。
a=2のとき2x^2-bx+c
|b|=6,6^2-4・2・c=40
|b|=7,7^2-4・2・c=40
|b|=8,8^2-4・2・c=40,C=3
a=12のとき12x^2-bx+c
|b|=36,36^2-4・12・c=1300
|b|=37,37^2-4・12・c=1300
|b|=38,38^2-4・12・c=1300,c=3
a=70のとき70x^2-bx+c
|b|=210,210^2-4・70・c=44104
|b|=211,211^2-4・70・c=44104
|b|=212,212^2-4・70・c=1300,c=3
(3a+2)^2-4a・3=(9a^2+4)が成り立つ
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√5/1→x^2-x-1
√8/2→x^2-2x-1
√221/5→5x^2-11x-5
√1517/13→13x^2-29x-13
√7565/29→29x^2-63x-31・・・ペル
√10400/34→17x^2-38x-17
√71285/89→89x^2-199x-89
√257045/169→169x^2-367x-181・・・ペル
√338720/194→97x^2-216x-98・・・どちらでもない
√488597/233→233x^2-521x-233
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λ>3に対して
√13/1→x^2-3x-1=0
√85/3→3x^2-7x-3=0
√580/8→8x^2-18x-8=0=0
√3973/21→21x^2-47x-21=0
√27229/55→55x^2-123x-55=0
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2x^2-8x+3=0
x=(4+√ 10)/2
x=3+{-2+√10)}/2+++
x=3+1/(2/{-2+√ (10)})
x=3+1/({2+√ 10)}/3)
x=3+1/(1+{-1+√ (10)}/3)
x=3+1/(1+1/(3/{-1+√ (10)})
x=3+1/(1+1/({1+√ 10)}/3)
x=3+1/(1+1/(1+{-2+√ (10)}/3)
x=3+1/(1+1/(1+1/(3/{-2+√ (10)})
x=3+1/(1+1/(1+1/({2+√ (10)}/2)
x=3+1/(1+1/(1+1/(2+{-2+√ 10)}/2)+++
x=3+1/(1+1/(1+1/(2+1/(2/{-2+√ (10)})
x=3+1/(1+1/(1+1/(2+1/({2+√ (10)}/3)
x=3+1/(1+1/(1+1/(2+1/(1+{-1+√ (10)}/3)
x=3+1/(1+1/(1+1/(2+1/(1+1/(3/{-1+√(10)})
x=3+1/(1+1/(1+1/(2+1/(1+1/({1+√(10)}/3)
x=3+1/(1+1/(1+1/(2+1/(1+1/(1+{-2+√ (10)}/3)
x=3+1/(1+1/(1+1/(2+1/(1+1/(1+1/(3/{-2+√(10)})
x=3+1/(1+1/(1+1/(2+1/(1+1/(1+1/({2+√10)}/2))
x=3+1/(1+1/(1+1/(2+1/(1+1/(1+1/(2+{-2+√(10)}/2))+++
x=3+1/(1+1/(1+1/(2+1/(1+1/(1+1/(2+1/(2/{-2+√(10)})
x=3+1/(1+1/(1+1/(2+1/(1+1/(1+1/(2+1/{2+√ (10)}/3)
x=3+1/(1+1/(1+1/(2+1/(1+1/(1+1/(2+1/(1+{-1+√ 10)}/3)
x=3+1/(1+1/(1+1/(2+1/(1+1/(1+1/(2+1/(1+1/(3/{-1+√(10)})
x=3+1/(1+1/(1+1/(2+1/(1+1/(1+1/(2+1/(1+1/{1+√ (10)})/3}
x=3+1/(1+1/(1+1/(2+1/(1+1/(1+1/(2+1/(1+1/(1+{-2+√ (10)})/3}
x=3+1/(1+1/(1+1/(2+1/(1+1/(1+1/(2+1/(1+1/(1+1/(3/{-2+√ 10)})
x=3+1/(1+1/(1+1/(2+1/(1+1/(1+1/(2+1/(1+1/(1+1/({2+√(10)}/2)
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x=[3:1,1,2,---1,1,2---,2,1,1,1,1,2,2,1,1,2,・・・]
x-3=1/(1+(1/1+1/(2+(x-3))
x-3=1/(1+(1/1+1/(x-1))
x-3=1/(1+(x-1)/(x))
(x-3)=x/(2x-1)
(x-3)(2x-1)=x
2x^2-7x+3=x・・・(OK)
しかし
y=(-4+√ 10)/2・・・負になってしまう。ペル型は存在しないのかもしれない。
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a=2のとき2x^2-8x+3
x=(8+√40)/4>3
y=(-8+√40)/4<0
a=12のとき12x^2-38x+3
x=(38+√1300)/24>3
y=(-38+√1300)/24<
a=70のとき70x^2-212x+3
x=(212+√44104)/140>3
y=(-212+√44104)/140<0
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