how can i find x value from given y (6th degree polynomial)

조회 수: 3 (최근 30일)
firrou bouteflika
firrou bouteflika 2021년 7월 9일
댓글: firrou bouteflika 2021년 12월 19일
y = [7 12 18 27 35 39];
p1 = 3.7739e-21
p2 = -6.5969e-17
p3 = 2.2715e-13
p4 = 1.1034e-09
p5 = -4.8986e-06
p6 = 0.010416
p7 = -0.70896
y = p1*x^6 + p2*x^5+p3*x^4+p4*x^3+p5*x^2+p6*x+p7;

채택된 답변

Matt J
Matt J 2021년 7월 9일
x=roots([p1,p2,p3,p4,p5,p6,p7-y])
  댓글 수: 9
Walter Roberson
Walter Roberson 2021년 12월 19일
format long g
p = [3.7769e-21, -6.6055e-17, 2.2806e-13, 1.0989e-09, -4.8887e-06, 0.010408, -0.71229];
R = roots(p)
R =
9350.21416809902 + 1915.74457506144i 9350.21416809902 - 1915.74457506144i -4499.3555970064 + 0i 1608.69399831728 + 1978.77107818079i 1608.69399831728 - 1978.77107818079i 70.7499925489447 + 0i
realroots = R(imag(R)==0)
realroots = 2×1
1.0e+00 * -4499.3555970064 70.7499925489447
syms x
poly = poly2sym(p)
poly = 
fplot([poly,0], [-4750 250])
It is a degree 6 polynomial in real coefficients. There are always going to be an even number of real roots: in this case there are two real roots. You can never get just one real root for a polynomial of even order that has real coefficients.
firrou bouteflika
firrou bouteflika 2021년 12월 19일
i see thank you and i just realized i can use polyval
h = polyval(p,[16.27 27.9 41.86 62.79 81.39 90.69])

댓글을 달려면 로그인하십시오.

추가 답변 (0개)

카테고리

Help CenterFile Exchange에서 Logical에 대해 자세히 알아보기

태그

제품


릴리스

R2012a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by