How do I fill in a shape made by three lines?

I'm trying to fill in a shape created by three lines: y=x^2; y=(-1/4)x+9/2; y=0. I still don't clearly understand the "fill" command and I can't find anything that would allow me to fill in this area. I could use some help and if you could explain what's going on and why.

As of right now, I've nothing in the fill section on my code, but I was instructed that it is supposed to come before the plot. This is my code so far:

%Supplement Problem 4
x=[0:0.5:20];
y=x.^2;
y2=x.*(-1./4)+(9./2);
y3=x.*0;

%Fill in the Shape

%Figure
plot(x,y,x,y2,x,y3); grid on;
axis([-1,20,-1,5])

Answer 1

[Image Analyst]

Close. But try this:

%Supplement Problem 4
x=[0:0.5:20];
y=x.^2;
y2=x.*(-1./4)+(9./2);
y3=x.*0;

%Fill in the Shape
y4 = min([y;y2]);
%Figure
plot(x,y,x,y2,x,y3); grid on;
axis([-1,20,-1,5])
hold on;
area(x, y4, 'FaceColor', [0.7, 0.2, 0.8])

[Sonia Sanchez]

Thanks. That worked. Not sure how, but it did.