MATLAB: Equation and its tangent with x

Question

The following code finds the tangent of a function which is y=x*x+2x at point x1=1 and plots both function and its tangent. The code includes the equation of the tangent line which is z(x) function. My problem is that I need to plot the same graph for x1=1 x1=2 and x1=3 in the same figure..

When I change 4th line x1=1:3 then there is an error.

thanks for comments please do not think that it is a math problem… best wishes,

____________________

syms x f(x) z(x)

f(x)=x.*x+2*x

df=diff(f,x)

x1=1:1

m=df(x1)

z1=f(x1)

z(x)=z1+(m*(x-x1))

figure

x=-7:5;

plot (x,f(x),x,z(x))

hold on

Answer 1

syms x f(x) z(x) 
f(x)=x.*x+2*x;
df=diff(f,x);
x1=1:3;
m=df(x1);
z1=f(x1);
hold on
x=-7:.1:5;
plot(x,f(x));
for i=1:3
z = double(z1(i))+(double(m(i))*(x-x1(i)));
plot(x,z);
end