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本帖最后由 风花飘飘 于 2018-1-17 13:58 编辑
【解高次方程的“降次之路”!】【四元、五元、天元辗转降次消元术…… 】
缺4次项方程:x^5+a*x^3+b*x^2+c*x+d=0---------(0) 的5个根,其必和等于0。
不妨设为:x1=r-s; x2=s-t; x3=t-u; x4=u-v; x5=v-r
表达式1: (x-r+s)*(x-s+t)*(x-t+u) = x^3+(u-r)*x^2+((t-r)*u-t^2+s*t-s^2+r*s)*x+((s-r)*t-s^2+r*s)*u+(r-s)*t^2+(s^2-r*s)*t
x3+(u−r)x2+((t−r)u−t2+st−s2+rs)x+((s−r)t−s2+rs)u+(r−s)t2+(s2−rs)t
表达式2: (x-u+v)*(x-v+r) = x^2+(r-u)*x-v^2+(u+r)*v-r*u
x2+(r−u)x−v2+(u+r)v−ru
表达式2乘以表达式1:
(x^2+(r-u)*x-v^2+(u+r)*v-r*u)*(x^3+(u-r)*x^2+((t-r)*u-t^2+s*t-s^2+r*s)*x+((s-r)*t-s^2+r*s)*u+(r-s)*t^2+(s^2-r*s)*t) = x^5+(-v^2+(u+r)*v-u^2+t*u-t^2+s*t-s^2+r*s-r^2)*x^3+((r-u)*v^2+(u^2-r^2)*v-t*u^2+t^2*u-s*t^2+s^2*t-r*s^2+r^2*s)*x^2+(((r-t)*u+t^2-s*t+s^2-r*s)*v^2+((t-r)*u^2+(-t^2+(s+r)*t-s^2+r*s-r^2)*u-r*t^2+r*s*t-r*s^2+r^2*s)*v+(-s*t+s^2-r*s+r^2)*u^2+(s*t^2+(-s^2+r*s-r^2)*t)*u+(r^2-r*s)*t^2+(r*s^2-r^2*s)*t)*x+(((r-s)*t+s^2-r*s)*u+(s-r)*t^2+(r*s-s^2)*t)*v^2+(((s-r)*t-s^2+r*s)*u^2+((r-s)*t^2+(s^2-r^2)*t-r*s^2+r^2*s)*u+(r^2-r*s)*t^2+(r*s^2-r^2*s)*t)*v+((r^2-r*s)*t+r*s^2-r^2*s)*u^2+((r*s-r^2)*t^2+(r^2*s-r*s^2)*t)*u
x5+(−v2+(u+r)v−u2+tu−t2+st−s2+rs−r2)x3+((r−u)v2+(u2−r2)v−tu2+t2u−st2+s2t−rs2+r2s)x2+(((r−t)u+t2−st+s2−rs)v2+((t−r)u2+(−t2+(s+r)t−s2+rs−r2)u−rt2+rst−rs2+r2s)v+(−st+s2−rs+r2)u2+(st2+(−s2+rs−r2)t)u+(r2−rs)t2+(rs2−r2s)t)x+(((r−s)t+s2−rs)u+(s−r)t2+(rs−s2)t)v2+(((s−r)t−s2+rs)u2+((r−s)t2+(s2−r2)t−rs2+r2s)u+(r2−rs)t2+(rs2−r2s)t)v+((r2−rs)t+rs2−r2s)u2+((rs−r2)t2+(r2s−rs2)t)u
以上无误!
继续演绎…………
对于缺4次项方程:
令:y1=x-x1; y2=x-x2; y3=x-x3; y4=x-x4; y5=x-x5---------(0.1)
将(0.1)分别代入(0),分别得到关于yi的(i=1,2,3,4,5)共5个方程:
毫无疑问,yi是 (i=1,2,3,4,5)等于0滴!
所以,这5个方程的常数表达式必须是等于0滴!
即:
-s^5+5*r*s^4+(-10*r^2-a)*s^3+(10*r^3+3*a*r+b)*s^2+(-5*r^4-3*a*r^2-2*b*r-c)*s+r^5+a*r^3+b*r^2+c*r+d =0--------------(1)
-t^5+5*s*t^4+(-10*s^2-a)*t^3+(10*s^3+3*a*s+b)*t^2+(-5*s^4-3*a*s^2-2*b*s-c)*t+s^5+a*s^3+b*s^2+c*s+d=0-------------(2)
-u^5+5*t*u^4+(-10*t^2-a)*u^3+(10*t^3+3*a*t+b)*u^2+(-5*t^4-3*a*t^2-2*b*t-c)*u+t^5+a*t^3+b*t^2+c*t+d=0----------------(3)
-v^5+5*u*v^4+(-10*u^2-a)*v^3+(10*u^3+3*a*u+b)*v^2+(-5*u^4-3*a*u^2-2*b*u-c)*v+u^5+a*u^3+b*u^2+c*u+d=0---------------(4)
+v^5-5*r*v^4+(10*r^2+a)*v^3+(-10*r^3-3*a*r+b)*v^2+(5*r^4+3*a*r^2-2*b*r+c)*v-r^5-a*r^3+b*r^2-c*r+d=0-------------------------(5)
联立(4)(5)
+v^5-5*r*v^4+(10*r^2)*v^3+(-10*r^3)*v^2+(5*r^4-5)*v-r^5+5*r-2=0-------------------------(5)
得(6)
(5*u-5*r)*v^4+(10*r^2-10*u^2)*v^3+(10*u^3-10*r^3)*v^2+(5*r^4-5*u^4)*v+u^5-5*u-r^5+5*r-4=0--------------------------(6)
联立(6)(3),得(7)
(5*u-5*r)*v^4+(10*r^2-10*u^2)*v^3+(10*u^3-10*r^3)*v^2+(5*r^4-5*u^4)*v+5*t*u^4+(-10*t^2-a)*u^3+(10*t^3+3*a*t+b)*u^2+(-5*t^4-3*a*t^2-2*b*t-c-5)*u+t^5+a*t^3+b*t^2+c*t-r^5+5*r+d-4=0-----------------------(7)
到此,大家当然可以联立(6)(7)啦~(5)(7)啦~等等啦~,暂不为也!
继续:
联立(7)(2),得(8)
(待续…………)
另杂联:
继续:
联立(7)(5),得(11)
-v^5+5*u*v^4-10*u^2*v^3+10*u^3*v^2+(5-5*u^4)*v+5*t*u^4+(-10*t^2-a)*u^3+(10*t^3+3*a*t+b)*u^2+(-5*t^4-3*a*t^2-2*b*t-c-5)*u+t^5+a*t^3+b*t^2+c*t+d-2-------------(11)
联立(4)(11)得(12)
a*v^3+(-3*a*u-b)*v^2+(3*a*u^2+2*b*u+c+5)*v-u^5+5*t*u^4+(-10*t^2-2*a)*u^3+(10*t^3+3*a*t)*u^2+(-5*t^4-3*a*t^2-2*b*t-2*c-5)*u+t^5+a*t^3+b*t^2+c*t-2=0--------(12)
联立(12)(3)
得(13)
a*v^3+(-3*a*u-b)*v^2+(3*a*u^2+2*b*u+c+5)*v-a*u^3-b*u^2+(-c-5)*u-d-2=0-------(13) |
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