MATLAB: Hope the plotting graph

plot

x = linspace(20,100000);

y = 20*log(1/(1+(2*(3.14)*(x.)*(102*10^-9)*(985.1))^2)^0.5);

plot(x,y)

the matlab said like the below~~~~~~~~~ whats the matter?

error: parse error:

syntax error

>>> y = 20*log(1/(1+(2*(3.14)*(x.)*(102*10^-9)*(985.1))^2)^0.5);

error: 'y' undefined near line 1, column 1

Try this

x = linspace(20,100000); 
y = 20*log(1./(1+(2*(3.14)*(x)*(102*10^-9)*(985.1)).^2).^0.5);
plot(x,y)