hi, i need to run this code and plot it properly

clear all;

clc;

close all;

u=[2 0 1 5 1 7 4 3 3];

n=max(u);

m=mean(u);

syms x p;

p=1200;

y=@(x)(x*(p-3*x));

gy=ezplot(y);

hold on

grid on

df=diff(y(x),1);

xin=solve(y(x));

xint=[xin,zeros(length(xin),1)];

yin=[0,y(0)];

plot(xint(:,1),xint(:,2),'+');

plot(yin(:,1),yin(:,2),'+');

hold on

crit=solve(df);

critp=[crit,y(crit)];

plot(critp(:,1),critp(:,2))

hold on

dff=diff(y(x),2);

inf=solve(dff);

infp=[inf,y(inf)];

plot(infp(:,1),infp(:,2));

Answer 1

[Walter Roberson]

Your function y(x) is a quadratic function.

The first derivative of y(x) is linear so it is possible to solve() that.

But the second derivative of a quadratic function is a constant. That constant is either equal to 0 or it is not equal to 0, so you cannot solve() the second derivative.

Also you have

inf=solve(dff);

which overwrites the normal inf() function in MATLAB which stands for infinity. Although MATLAB allows you to create a variable with the same name as the infinity function, doing that is quite confusing for the readers of your code. I have no idea what you are trying to determine at that point.

[Sadon Alathba]

Thanks Walter for providing a good answer. Guess I added the second derivative by mistake, and as always Thank You :)