Plot the Relative Error

I don't know what the relative error is or how to calculate it. I feel as if I'm missing something with part (a), but I don't know where to even begin with part (b).

V = [10 20 30 40 50 60 70 80];
F_D = [25 70 380 550 610 1220 830 1450];
plot(V,F_D)

Answer 1

[David Hill]

V = [10 20 30 40 50 60 70 80];
v=10:.1:80;
f=@(x).2741*x.^1.9842;
F_D = [25 70 380 550 610 1220 830 1450];
plot(V,F_D,v,f(v));
figure;
plot(V,abs((f(V)-F_D)./f(V)));