2021-07-13 09:49:07 +0200 received badge ● Notable Question (source) 2021-07-13 09:49:07 +0200 received badge ● Popular Question (source) 2019-05-02 23:49:50 +0200 asked a question plot3d a symbolic function that has ln in it I have this function  ft1 = x1^2 + x1*x2 + 1.5*x2^2 - 2*ln(x1) - ln(x2)  when i call this line in order to plot the ft1 ploter = plot3d(ft1, (-1/3*sqrt(3)*sqrt(2), 1/3*sqrt(3)*sqrt(2)), (-1/3*sqrt(3)*sqrt(2), 1/3*sqrt(3)*sqrt(2)), adaptive = True, mesh = True, dots = True)  i get this error ValueError: cannot convert float NaN to integer What should i do in order to plot the ft1 ? 2019-04-19 09:38:41 +0200 received badge ● Nice Question (source) 2019-04-17 10:21:51 +0200 commented answer General solution for a matrix Thank you, you give a good idea on how to solve my problem 2019-04-17 10:21:22 +0200 answered a question General solution for a matrix Ok i also had this equation for p p = Q*x - b  and i replace x in that equation and that it is how i got the answer that i wanted I think that sagemath wants to use matrices with multiplication not as a place that you can throw a function 2019-04-17 09:12:11 +0200 received badge ● Editor (source) 2019-04-17 09:03:35 +0200 commented answer General solution for a matrix Thank you but i did make a wrong use of the word solution I want to replace the x1 and x2 with numbers and use that result on something else So on the example before i want to get the result of [14, 6] 2019-04-17 08:29:04 +0200 received badge ● Student (source) 2019-04-17 08:18:34 +0200 asked a question General solution for a matrix I have a matrix named p and with the values [-10*x1 - 4*x2 + 14, -4*x1 - 2*x2 + 6]  When I try to solve the matrix with this line: print(p(p.arguments()[0] == 0, p.arguments()[1] == 0))  I get this error: ValueError: use named arguments, like EXPR(x=..., y=...)  In general i want to use something like this, the arguments are x1 and x2 and the x is a list of numbers that it will change on every loop print(p([i == j for i,j in zip(f.arguments(), x)]))  But it reproduce the same error 2019-04-17 08:18:34 +0200 asked a question General solutions for a matrix I have a matrix named p and with the values [-10x1 - 4x2 + 14, -4x1 - 2x2 + 6] when i try to solve the matrix with this line: "print(p(p.arguments()[0] == 0, p.arguments()[1] == 0))" i get this error: ValueError: use named arguments, like EXPR(x=..., y=...) I want to provide a general solutions any ideas ?