Axis length

I need a quadratic plot, means the x-axis and y-axis should have the same length. But root always plots a long x-axis and a shorter y-axis. I don’t mean the scale of the axis. I have the same scale on both axis.
Is there any command to get this?
And a second question… I would like to include a number in the plot. The number is calculated during the plotting process. I know possibilities to include text in the plot, but how do I include a variable?
thanks for help and
best regards

You should create a square TCanvas, or a square TPad in a rectangular TCancas.

To draw a variable as a TText use, Form():

text->DrawText(x, y, Form("%g",val));