Help me plot the solution in graph

Consider the following system of equations: 9 − 2y − x = 0; −x + 2y = 13.

Use MATLAB to solve the above system of equations. Then, plot the solution and comment on the slope and the shape of the equations.

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Answer 1

[Walter Roberson]

A = randi([-9,9])

A = -8

B = randi([-9,9])

B = -4

C = randi([-9,9])

C = -5

fun1 = @(x,y) A*x + B*y + C

fun1 = function_handle with value:
    @(x,y)A*x+B*y+C

A2 = randi([-9,9])

A2 = 1

B2 = randi([-9,9])

B2 = 7

C2 = randi([-9,9])

C2 = -1

fun2 = @(x,y) A2*x + B2*y + C2

fun2 = function_handle with value:
    @(x,y)A2*x+B2*y+C2

fimplicit(fun1);
hold on
fimplicit(fun2);
hold off

The solution to the system is at the intersection of the two lines.

Answer 2

[Sam Chak]

Hi @Hung,

I'll show you another two ways of plotting the line equations.

syms x y

% specify the two line equations
eqn1   = 9 - 2*y - x == 13;     % equation 1
eqn2   =     2*y - x == 0;      % equation 2

Method 1: Using ezplot()

yLine1 = isolate(eqn1, y)

yLine1 = 

yLine2 = isolate(eqn2, y)

yLine2 = 

figure(1)
h1 = ezplot(yLine1, [-6, 6, -5, 3]); 
h1.Color = 'blue'; hold on
h2 = ezplot(yLine2, [-6, 6, -5, 3]); 
h2.Color = 'red';  hold off
grid on
title('Method 1: using "ezplot"')

Method 2: Using fplot()

soly1  = solve(eqn1, y)

soly1 = 

soly2  = solve(eqn2, y)

soly2 = 

figure(2)
fplot(soly1, [-6, 6]), hold on
fplot(soly2, [-6, 6]), grid on
xlabel('x'), ylabel('y')
title('Method 2: using "fplot"')