I'm writing this answer on a mobile phone and thus, I havn't checked this code, but it should work:
clc
clear all
v0=50:1:100;
i=1
syms t v0
eqn1 = (0 == v0-12.*(t-0.75)-v0+9.*t);
time=solve(eqn1,t)
syms d v0
eqn2 = (0 == ((v0.*0.75)+(v0.*time)-(v0.*0.75)+0.5.*(-12).*(time-0.75)^2-d-v0.*time+0.5.*(9).*time^2));
distance=solve(eqn2,d)
plot(v0, distance);
hold on;
If it doesn't works, try putting the whole block inside for loop and iterate on individual values of v0. But, I think this method should also work.
You can also use fplot whose documentation can be found here: https://in.mathworks.com/help/matlab/ref/fplot.html
Hope that helps!
