Output from startCalc:
 26 x^2 - 91 xy - 26 y^2 - 58 x - 59 y - 71 = 0

by Dario Alejandro Alpern

First of all we must determine the gcd of all coefficients but the constant term, that is: gcd(26, -91, -26, -58, -59) = 1.

Dividing the equation by the greatest common divisor we obtain:
 26 x^2 - 91 xy - 26 y^2 - 58 x - 59 y - 71 = 0

We try now to solve this equation module 9, 16 and 25.

There are solutions, so we must continue.

We want to convert this equation to one of the form:
x´^2 + B y^2 + C y + D = 0

Multiplying the equation by 104:
 2704 x^2 - 9464 xy - 2704 y^2 - 6032 x - 6136 y - 7384 = 0

 2704 x^2 + ( - 9464 y - 6032)x + ( - 2704 y^2 - 6136 y - 7384) = 0

To complete the square we should add and subtract:
( - 91 y - 58)^2

Then the equation converts to:
( 52 x - 91 y - 58)^2 + ( - 2704 y^2 - 6136 y - 7384) - ( 8281 y^2 + 10556 y + 3364) = 0

( 52 x - 91 y - 58)^2 + ( - 10985 y^2 - 16692 y - 10748) = 0

Now we perform the substitution:
x´ =  52 x - 91 y - 58

This gives:
 x´^2 - 10985 y^2 - 16692 y - 10748 = 0

Multiplying the equation by -65:
- 65 x´^2 + 714025 y^2 + 1084980 y + 698620 = 0

- 65x´^2 +( 714025 y^2 + 1084980 y) + 698620 = 0

- 65x´^2 +((-845)^2 y^2 + 2*(-845)*(-642) y) + 698620 = 0

Adding and subtracting (-642)^2:
- 65x´^2 +((-845)^2 y^2 + 2*(-845)*(-642) y + (-642)^2) + 698620 - (-642)^2 = 0

- 65x´^2 +( - 845 y - 642)^2 + 286456 = 0

Making the substitution y´ = - 845 y - 642:
- 65 x´^2 + y´^2 + 286456 = 0

We have to find the continued fraction expansion of the roots of 1 t^2 - 91 t - 676 = 0, that is, (sqrt(10985) + 91) / 2

The continued fraction expansion is:
97+ //1, 9, 2, 25, 1, 2, 1, 1, 1, 6, 1, 5, 1, 2, 7, 7, 2, 1, 5, 1, 6, 1, 1, 1, 2, 1, 25, 2, 9, 1, 103//
where the periodic part is marked in bold (the period has 31 coefficients).

We have to find the continued fraction expansion of the roots of -65 t^2 + 1 = 0, that is, sqrt(260) /(-130)

Simplifying, sqrt(65) / (-65)

The continued fraction expansion is:
-1+ //1, 7, 16//
where the periodic part is marked in bold.

- 65 x^2 + y'^2 + 286456 = 0

Let x' = sy' - f'z, so [-(as^2 + bs + c)/f']y'^2 + (2as + b)y'z - af'z^2 = 1.

So - 65 s^2 +1 should be multiple of 286456.

This holds for s = 61031, 204259, 132645, 275873, 65727, 208955, 137341, 280569, 5887, 149115, 77501, 220729, 10583, 153811, 82197, 225425.

Since 2 * 2 is a divisor of the constant term (286456), the solutions should be 2 times the solutions of - 65 u^2 + v^2 + 71614 = 0. Let F be the constant term.

- 65 x^2 + y'^2 + 71614 = 0

Let u = sv - Fz, so [-(as^2 + bs + c)/F]v^2 + (2as + b)vz - aFz^2 = 1.

So - 65 s^2 +1 should be multiple of 71614.

This holds for s = 61031, 65727, 5887, 10583.

Xn+1 = P Xn + Q Yn + K
Yn+1 = R Xn + S Yn + L

In order to find the values of P, Q, R, S we have to find first an integer solution of the equation m^2 + bmn + acn^2 =  m^2 - 91 mn - 676 n^2 = 1.

We have to find the continued fraction expansion of the roots of 1 t^2 - 91 t - 676 = 0, that is, (sqrt(10985) + 91) / 2

The continued fraction expansion is:
97+ //1, 9, 2, 25, 1, 2, 1, 1, 1, 6, 1, 5, 1, 2, 7, 7, 2, 1, 5, 1, 6, 1, 1, 1, 2, 1, 25, 2, 9, 1, 103//
where the periodic part is marked in bold (the period has 31 coefficients).

An integer solution of the equation m^2 + bmn + acn^2 =  m^2 - 91 mn - 676 n^2 = 1 is:

m = -20 959202 739850 883948 245647 530545 (32 digits)
n = -214077 649120 834543 562852 106272 (30 digits)

Using the formulas:
P = m
Q = -Cn

K =CD(P+S-2) + E(B-Bm-2ACn)
4AC-B2

R = An
S = m + Bn
L =D(B-Bm-2ACn) + AE(P+S-2)
4AC - B2
+ Dn

we obtain:

P = -20 959202 739850 883948 245647 530545 (32 digits)
Q = -5 566018 877141 698132 634154 763072 (31 digits)
K = -8 718342 976376 307924 004248 001090 (31 digits)
R = -5 566018 877141 698132 634154 763072 (31 digits)
S = -1 478136 669854 940484 026105 859793 (31 digits)
L = -2 315281 844744 993080 179339 614324 (31 digits)

Another integer solution of the equation m^2 + bmn + acn^2 =  m^2 - 91 mn - 676 n^2 = 1 is:

m = -1 478136 669854 940484 026105 859793 (31 digits)
n = 214077 649120 834543 562852 106272 (30 digits)

Using the formulas:
P = m
Q = -Cn

K =CD(P+S-2) + E(B-Bm-2ACn)
4AC-B2

R = An
S = m + Bn
L =D(B-Bm-2ACn) + AE(P+S-2)
4AC - B2
+ Dn

we obtain:

P = -1 478136 669854 940484 026105 859793 (31 digits)
Q = 5 566018 877141 698132 634154 763072 (31 digits)
K = 3 912238 321752 930146 204026 268958 (31 digits)
R = 5 566018 877141 698132 634154 763072 (31 digits)
S = -20 959202 739850 883948 245647 530545 (32 digits)
L = -14 731785 493753 396606 824761 778100 (32 digits)

Calculation time: 0h 0m 0s

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