How do I type this equation?

I need to write the equation

P = (10/(R+20))^2

When R starts at 0 and ends at 40 with step size of 0.1. So far, I have

R = [0:0.1:40];
P = R * (10/(R + 20))^2.

I've tried a few different ways, and I keep getting error message Matrix Dimensions Must Agree. How would I do this? I'm still very new to Matlab and I'm don't understand how everything works.

Answer 1

[Walter Roberson]

    P = R .* (10./(R + 20)).^2.