clc
clear
a=1.21;
b=2.04;
c=1.72;
d=0.85;
f=17.83;

x=1+(a/b)+(c/f^2)

r=1/(1/a)+(1/b)+(1/c)+(1/d)

s=b-a/d-c

y=a*b*(1/c)*(f^2/2)