How to graph a quadratic function f(x,y) - parabola

The intention is to plot the next equation: 0==-(x+y).^2+6540.*(y.*2.6284 - x.*2.187) and get the following parabola:

I've tried several options, but I'm not able to get the parabola, what could I do?

Answer 1

[Walter Roberson]

Starting in R2016b, https://www.mathworks.com/help/matlab/ref/fimplicit.html

f = @(x,y) (x+y).^2 + 6540 * (y * 2.6284 - x * 2.187);
fimplicit(f, [-5000, 20000, -20000, 5000])

Answer 2

[Khairul Azam]

i tided to alive