# manipulation of parameter in a plot 2d function

In Mathematica is possible to plot a function of variables and parameters, giving the possibility to have a slider to change interactively the parameter values. For example this input *Manipulate[Plot[1-a/x, {x, 0, 10}], {a, 0, 20}]* outputs the plot of the function *1-a/x*, where **x** is the variable, so values are on the x-axis, and **a** is a parameter and it's exact value is set on a slide bar, between 0 and 20, that appears with running.
I tried to do that with Sage, using the @interact possibility but I cannot find a solution for that. Could someone help me?