Please someone solve me error of matrix dimension for focal lengths equation

clear all;

close all;

clc;

n1=1.49;

n2=1:.1:2.42;

r1=.25;

r2=.50;

f=(((n1/n2)-1)*((1/r1)-(1/r2)))^-1;

fl=1/f;

plot(n2,fl);

xlabel('Refractive indices of surrounding material');

ylabel('Focal length');

title('Different focal lenths for varying refractive indices of different 
materials')

Answer 1

[Walter Roberson]

f = (((n1./n2)-1)*((1/r1)-(1/r2))).^-1;
fl = 1./f;

Though since the .^-1 is the same as 1/ I do not know why you do not just directly calculate

 fl = (((n1./n2)-1)*((1/r1)-(1/r2)));