3.12 For the discrete-time pulse
p[n]={(1,-1<=n<=1),(0 otherwise ):}
plot the convolutions p_(1)[n]=(p*p)[n] and p_(2)[n]=(p*p*p)[n]. Find closed-
form expressions for the Fourier transforms P(e^(j\omega )),P_(1)(e^(j\omega )), and P_(2)(e^(j\omega )), and
handsketch these.