Graphing a system of equations on the same set of axes

Here is my question to solve: Graph the following system on the same set of axes.

{y=(-2/3)*x + 4/3 {y= -(x^2)/3 + 3 {y= 2*x +9

Any suggestions are welcome!

Answer 1

[Matt Fig]

x = -10:.1:10;
y1 =(-2/3)*x + 4/3; 
y2 = -(x.^2)/3 + 3; 
y3 = 2*x +9;
plot(x,y1,'b',x,y2,'r',x,y3,'k')