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[求助]
用 Mathematica 分解因式
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請教: 如何在實數(shù)(實代數(shù)數(shù))范圍內(nèi)將整系數(shù)高次多項式分解為一次式與不可再分解的二次式的乘積?比如將 x^4+1 分解為 (x^2-√2 x+1)(x^2+√2 x+1)。以及類似地將有理分式分解為部分分式。 |
金蟲 (著名寫手)
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上面代碼顯示好像不對 下面這個 f[x_] := x^7 + 2 t1 = x /. Solve[f[x] == 0, x]; t1 = DeleteCases[t1, x_ /; Element[x, Reals]]; t2 = x /. Solve[f[x] == 0, x, Reals]; r1 = Table[ Solve[ComplexExpand[Im[t1[]^2 - a*t1[] + b]] == 0, a], {i, 1, Length[t1]}] // Flatten; r1 = DeleteDuplicates[r1]; r2 = Table[ Solve[ComplexExpand[Re[t1[]^2 - a*t1[] + b]] == 0, b], {i, 1, Length[t1]}] // Flatten; r2 = DeleteDuplicates[r2]; r3 = Table[{r1[], r2[] /. r1[]}, {i, 1, Length[r1]}]; ff1 = Table[temp1 = x^2 - a*x + b /. r3[] // Expand; Print[temp1]; temp1, {i, 1, Length[r3]}]; ff2 = Table[temp1 = x - t2[]; Print[temp1]; temp1, {i, 1, Length[t2]}]; ff = Join[ff1, ff2]; Apply[Times, ff] Apply[Times, ff] // N // Chop |

金蟲 (著名寫手)
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我寫了個很笨的代碼求這個問題 可能內(nèi)部有非常簡潔的方法 另外 也沒怎么優(yōu)化 看樣子 能求你說的情況 ---------code------------- Clear["Global`*"]; f[x_] := x^7 + 2 t1 = x /. Solve[f[x] == 0, x]; t1 = DeleteCases[t1, x_ /; Element[x, Reals]]; t2 = x /. Solve[f[x] == 0, x, Reals]; r1 = Table[ Solve[ComplexExpand[Im[t1[]^2 - a*t1[] + b]] == 0, a], {i, 1, Length[t1]}] // Flatten; r1 = DeleteDuplicates[r1]; r2 = Table[ Solve[ComplexExpand[Re[t1[]^2 - a*t1[] + b]] == 0, b], {i, 1, Length[t1]}] // Flatten; r2 = DeleteDuplicates[r2]; r3 = Table[{r1[], r2[] /. r1[]}, {i, 1, Length[r1]}]; ff1 = Table[temp1 = x^2 - a*x + b /. r3[] // Expand; Print[temp1]; temp1, {i, 1, Length[r3]}]; ff2 = Table[temp1 = x - t2[]; Print[temp1]; temp1, {i, 1, Length[t2]}]; ff = Join[ff1, ff2]; Apply[Times, ff] Apply[Times, ff] // N // Chop ------------------------------------------------------ 結(jié)果: 解析形式: (x+Power[2, (7)^-1]) (x^2-Power[2, (7)^-1] x cos((3 \[Pi])/14) csc(\[Pi]/7)-2^(2/7) sin((3 \[Pi])/14)+2^(2/7) cos((3 \[Pi])/14) cot(\[Pi]/7)) (x^2-Power[2, (7)^-1] x sin(\[Pi]/7) sec(\[Pi]/14)+2^(2/7) cos(\[Pi]/7)+2^(2/7) sin(\[Pi]/7) tan(\[Pi]/14)) (x^2+Power[2, (7)^-1] x cos(\[Pi]/14) sec((3 \[Pi])/14)+2^(2/7) sin(\[Pi]/14)+2^(2/7) cos(\[Pi]/14) tan((3 \[Pi])/14)) 數(shù)值化: (x+1.10409) (x^2-1.9895 x+1.21901) (x^2-0.491366 x+1.21901) (x^2+1.37678 x+1.21901) |
金蟲 (著名寫手)
金蟲 (著名寫手)
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下面這個代碼應該可以直接copy過去運行 我用mathematica8.04 第一行的函數(shù)可以改成其他多項式 -------------------- f[x_] := x^7 + 2 t1 = x /. Solve[f[x] == 0, x]; t1 = DeleteCases[t1, x_ /; Element[x, Reals]]; t2 = x /. Solve[f[x] == 0, x, Reals]; eq1 := {ComplexExpand[Im[t1[]^2 - a*t1[] + b]] == 0}; r1 = Table[Solve[eq1, a], {i, 1, Length[t1]}] // Flatten; r1 = DeleteDuplicates[r1]; eq2 := {ComplexExpand[Re[t1[]^2 - a*t1[] + b]] == 0}; r2 = Table[Solve[eq2, b], {i, 1, Length[t1]}] // Flatten; r2 = DeleteDuplicates[r2]; r3 = Table[{r1[], r2[] /. r1[]}, {i, 1, Length[r1]}]; ff1 = Table[temp1 = x^2 - a*x + b /. r3[] // Expand; Print[temp1]; temp1, {i, 1, Length[r3]}]; ff2 = Table[temp1 = x - t2[]; Print[temp1]; temp1, {i, 1, Length[t2]}]; ff = Join[ff1, ff2]; N[Apply[Times, ff], 20] |
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