Plotting a function that is equal to 0.

Hello, I'm doing some QDA and I need to plot a function that looks like the one below but I cannot seem to find a way to do it? Does anyone know how to plot it?

0.651 - 0.728(x_1) - 0.552(x_2) - 0.006(x_1 * x_2) - 0.071(x_1)^2 +.170 (x_2)^2 = 0.

The curve should look like the 2nd to last one from https://onlinecourses.science.psu.edu/stat557/book/export/html/35

Any hint or suggestion is much appreciated

Answer 1

[sixwwwwww]

One way to plot this equation is using 'ezplot' as follow:

ezplot('0.651 - 0.728 * x - 0.552 * y - 0.006 * x * y - 0.071 * x^2 + .170 * y^2')

See following link for more information about ezplot:

http://www.mathworks.com/help/matlab/ref/ezplot.html

Answer 2

[Walter Roberson]

x_2 = 138/85 + (3/170) * x_1 +/- (1/170) * sqrt(-34494 + 125416 * x_1 + 12079 * x_1^2)