Hi, i need help about how to evaluate a diff result with values of variables, thank you

Example

syms x y;
f1=(x.^3)+(x*y.^2)-(5);

df1y=diff(f1,y);

x=2;
y=0.25;

d=subs(df1y(x,y)) % Here is what im trying to do, but it doesn´t work apparently

hope you guys can help me to find out, thanks

Answer 1

[Walter Roberson]

d = subs(df1y)

However, I recommend using different variable names, such as

syms x y
f1 = (x.^3)+(x*y.^2)-(5);
df1y = diff(f1,y);
X = 2;    %do not overwrite the symbolic names!
Y = 0.25;
d = subs(df1y, {x, y}, {X, Y})

[José López]

Hello Walter, thank you very much! it worked perfect :D