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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 ?

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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