[英]Solve polynomial equation for x in R
這可能非常簡單,但是如何使用R求解x的以下方程式? X應該是一個實數。
((4*x)^2+(2*x)^2+(1*x)^2+(0.5*x)^2+0.25)*((1 - 0.167)/0.167) = 1
簡短的答案是,該多項式在實數集中沒有根,您可以在R的一些幫助下從分析上看到這一點:
> #((4*x)^2+(2*x)^2+(1*x)^2+(0.5*x)^2+0.25)*((1 - 0.167)/0.167) = 1
>
> # first add up your coefficients
> coefs <- c(16 + 4 + 1+ .25 , .25)
> coefs
[1] 21.25 0.25
>
> # apply the second product
> coefs <- (coefs - 0.167*coefs)/0.167
> coefs
[1] 105.995509 1.247006
>
> # move the one from one side to another
>
> coefs <- coefs - c(0,1)
> coefs
[1] 105.995509 0.247006
>
> #106*x^2 + 1/4 = 0 has no solution in the set of real number
您可能還會考慮使用Ryacas
,它可以根據與計算機代數系統yacas的接口來處理/解決符號表達式。 當然,與例如Maple相比,yacas在執行更高級功能時的性能是有限的,但是,在您的情況下,它可以正常工作。
#Ryacas solves the equation and shows that there is only a complex solution
library("Ryacas")
yacas("Solve(((4*x)^2+(2*x)^2+(1*x)^2+(0.5*x)^2+0.25)*((1 - 0.167)/0.167) == 1, x)")
# expression(list(x == complex_cartesian(0, root(0.00688875/2.95610875, 2)),
# x == complex_cartesian(0, -root(0.00688875/2.95610875, 2))))
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