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Down## Equation of the third degree. Find similar branches

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mashinist (2001-12-16 23:16) [0]I’m here, it seems like everyone is already sick of it with my math, but still. Does anyone have a piece of code to solve a third-degree equation of the form ax ^ 3 + bx ^ 2 + cx + d = 0, with a, b, c, d: extended;

Help

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Builder (2001-12-17 02:35) [1]But isn’t it easier than fucking, sitting down and writing yourself?

Take any book on numerical methods - this is in the first section.

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mashinist (2001-12-17 11:58) [2]Does not work.

Already tried.

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Romkin (2001-12-17 12:19) [3]http://alglib.chat.ru/equat/index.html#cube

In my opinion, exhaustively

But, in general, equations above the second degree are usually solved not by exact formulas, but by algorithms for finding the roots of polynomials of the nth degree

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savva (2001-12-17 12:31) [4]this is what the block diagram editor suggested

`Procedure CubeEquation (a, b, c: real; var nr: byte; x: array [1..3] of real); // for some reason, the 8 parameters are not described for some reason)) you yourself will describe begin p: = - a * a / 3 + b; q: = 2 * a / 3 * a / 3 * a / 3-a * b / 3 + c; QH: = (p / 3) * (p / 3) * (p / 3) + (q / 2) * (q / 2); if QH = 0 then begin nr: = 3; AH: = abs (q / 2); if AH <> 0 then begin AH: = sign (q) * exp (ln (AH) / 3) end; x [1]: = 2 * AH-a / 3; x [2]: = - AH-a / 3; x [3]: = - AH-a / 3 end else begin if QH> 0 then begin AH: = - q / 2 + sqrt (QH); AH: = sign (AH) * exp (ln (abs (AH)) / 3); BH: = - q / 2-sqrt (QH); BH: = sign (BH) * exp (ln (abs (BH)) / 3); x [1]: = AH + BH-a / 3; if AH = BH then begin nr: = 3; x [2]: = - (AH + BH) / 2-a / 3; x [3]: = - (AH + BH) / 2-a / 3 end else begin nr: = 1; x [2]: = - (AH + BH) / 2-a / 3; x [3]: = (AH-BH) / 2 * sqrt (3) end; end else begin nr: = 3; u: = - q / 2 / sqrt (-p * p * p / 27); u: = arccos (u); x [1]: = 2 * sqrt (abs (p / 3)) * cos (u / 3) -a / 3; x [2]: = - 2 * sqrt (abs (p / 3)) * cos (u / 3 + Pi / 3) -a / 3; x [3]: = - 2 * sqrt (abs (p / 3)) * cos (u / 3-Pi / 3) -a / 3 end; end; end;`

I don’t know whether to trust ...

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SergVlad (2001-12-17 13:58) [5]To mashinist

Still struggling with your regulators?

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Юрий Зотов (2001-12-17 14:59) [6]> Romkin © (17.12.01 12: 19)

I allow myself an amendment - above the third, and not the second. For cubic equations, however, there are exact formulas - for example, the Cardano formula. It is much simpler, faster and more accurate.

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mashinist (2001-12-17 15:40) [7]Thank you!

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Nemesis

2001-10-08 13:02

2002.01.08

Mobile

1-22113

Yuraz

2001-12-19 20:25

2002.01.08

Brothers why

3-21934

Alexsyy

2001-12-04 08:52

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1-22138

Serg5

2001-12-20 09:22

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People, tell me, and how to clear Image1, Clear did not find the function ...

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Alexander

2001-11-05 13:20

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