2018-05-04 11:27:50 -0500 asked a question Solve a system Why this command doesn't give me any solution :  solve([2*x+y==0,x-2*y==1],x)  I suppose because, there is an unique solution and x doesn't depend on y. Now I would like to know when we solve an equation such that $$f(z)= 0\iff Re(x)+iIm(x)=0$$ with $z=x+iy$ and $f(z)=5z-i\overline{z}^2+3+2i$ real(x)=-2*x*y + 5*x + 3 im(x) = -x^2 + y^2 + 5*y + 2 solve([real(x)==0, im(x)==0], x)  Is this command the right one to solve this problem ? 2018-03-31 15:10:09 -0500 received badge ● Scholar (source) 2018-03-31 15:10:07 -0500 received badge ● Supporter (source) 2018-03-31 13:21:34 -0500 received badge ● Student (source) 2018-03-31 12:34:18 -0500 asked a question function created in python under sage Below a function in python, forget();var('n i');g(x)=sin(x)+tan(x); def maderive(n): for i in range(n): g=g.diff() return g  When I call this function maderive(3)  It doesn't work, I've got an error . 2018-03-14 16:10:48 -0500 asked a question place a point on a graph I 've got a graph as it is shown below: plot(f(x),-10,5 )  And I would like to place a point on (x,f(x))=(t_0,y_0)=(1,-1), with labels. How can I do that please? Thanks