Cubic graph

% M-file for drawing some cubic graphs y=x^3-ax+1 You need to input the lower and upper bounds of x and y on the screen, and also the value of a.

clg

xl=input('Type the lower bound of x ');
xu=input('Type the upper bound of x ');
yl=input('Type the lower bound of y ');
yu=input('Type the upper bound of y ');



a=input('Type the value of a ');

xstep=(xu-xl)/200;


x=xl:xstep:xu;
y=x.*x.*x - a*x + ones(size(x));

plot(x,y,'r')
axis([xl xu yl yu]);
hold on

u=[xl xu];
v=[0 0];
plot(u,v,'w')

hold off