Check impulse responses are inverses using convolution

I have written the following code to check that h1[n] and g[n] are inverses of each other by generating an impulse when I convolute them. However, I'm not currently getting an impulse.

The original transfer function is H(z) = (1-2.5*z^(-1)+z^(-2))/(1-z^(-1)+0.7z^(-2));

function part2b

n=-20:0;

g1 = -1.8*(2).^(n-1);

n=1:20;

g2=-0.3*(0.5).^(n-1);

g=[g1 g2];

g(21)=g(21)+1;

n=0:20;

h1 = 0.82*exp(1i*2.72)*(0.84*exp(1i*0.93)).^(n-1) + 0.82*exp(1i*-2.72)*(0.84*exp(1i*-0.93)).^(n-1);

h1(1)=h1(1)+1;

y=conv(h1,g);

x = -20:40;

stem(x,y)