Evaluating polynomial functions to get integer as answer

1 次查看（过去 30 天）
Rodrigo Toledo
Rodrigo Toledo 2021-4-4
编辑： Walter Roberson 2021-4-4
I am trying to evaluate:
syms x y
eq = (x^2 + y^3 == 31)
solve(eq)
eqs = [x^2 + y^3 == 31, x^2 == 31 - y^3]
S = solve(eq,[x y])
S.x and S.y still not 2 and 3
i am expecting to get as answer two integer: x=2 and y=3. How can i do it?
Thanks

请先登录，再回答此问题。

采纳的回答

Walter Roberson
Walter Roberson 2021-4-4
编辑：Walter Roberson 2021-4-4
Ran in:
syms x y integer
eq = (x^2 + y^3 == 31)
eq = 
solx = solve(eq,x,'returnconditions',true)
solx = struct with fields:
x: [2×1 sym] parameters: [1×0 sym] conditions: [2×1 sym]
soly = solve(solx.conditions)
soly = 
3
X = subs(solx.x,y,soly)
X = 
Y = soly
Y = 
3
Caution: this kind of process will not generally attempt to find more than one solution for solx.conditions. But you could
soly = solve(eq,y,'returnconditions',true)
soly = struct with fields:
y: [3×1 sym] parameters: [1×0 sym] conditions: [3×1 sym]
solx = arrayfun(@solve, soly.conditions, 'uniform', 0)
Warning: Unable to find explicit solution. For options, see help.
solx = 3×1 cell array
{0×1 sym} {2×1 sym} {0×1 sym}
X = solx{2}
X = 
Y = subs(soly.y(2), x, X)
Y = 

更多回答（1 个）

darova
darova 2021-4-4
solve can be used for simple problems. Use fsolve or vpasolve to get numerical results
  1 个评论
Walter Roberson
Walter Roberson 2021-4-4
Not the point. The point is that solve() is having difficulty processing integer constraints in this case. fsolve and vpasolve have no chance of processing integer constraints.

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Conversion Between Symbolic and Numeric 的更多信息

标签

产品

Community Treasure Hunt

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

Start Hunting!

Translated by