To attempt and solve a problem. This is my code:

%pdb.m
function dydx = pdb(x,y)
dydx=(-2*x^3)+(12*x^2)-(20*x)+(8.5);

%runpdb.m
clear
clc

rentang_x = [0 4];
y0 = 1;

[x,y] = ode23('pdb',rentang_x,y0);

plot(x,y)
xlabel('x')
ylabel('y')

the error is 
Error using pdb (line 3)
Not enough input arguments.

Answer 1

[Adam]

How are you running your code?

That is a function that takes arguments, not a script, so you must call it from the command line (or another script/function/class) passing arguments into it as e.g.

pdb( 6, 7 );

rather than just clicking 'Run' on the .m file.