How to use convolution in Matlab

Question

My problem is find the output to U(t+1)-U(t-1) with Matlab given the transfer function H(s).

I know that I should be able to find the output to any input of an LTI system when given H(s), so I tried using convolution to find the output and plot it. Below is my attempt at using the conv to produce the output. Ht= dirac(t) - 4*exp(-6*t)

syms s t b
Hs=(s+2)/(s+6)
Ht=ilaplace(Hs)
tt=0:.1:60
Hnum= subs(Ht, 't',[eps:.1:10]);
%turn symbolic vector into actual
A=double(Hnum);
input=ones(1, 501);

output=conv(input,A)
figure(3)
plot(tt,output)  

I also tried to use the integral way

 %b is tau 
 t1=0;
 t2=int(exp(-(6*b)),b,0,t+1)+1
 t3=int(exp(-(6*b)),b,t-1,t+1)

I know that H(t)*x(t) = y(t). I was not able to get any reasonable output for the graphs. Any hints or help are much appreciated.