Several ways you could do this. If your signal is represented as a discrete sequence, then just use a double loop, accumulating the result into a vector of appropriate length.
If you were intended to work on the signals in symbolic form, then a z-transform can also be used for convolution.
ztrans(exp(-3*t))
ans =
I showed that much to explain how to write an exponential. Note that the exponential you wrote will use the function exp in MATLAB.
Or, can you solve a convolution problem using the Laplace tranform? If this is a convolution INTEGRAL, as opposed to the sum implied by a discretized signal, then Laplace transforms would be appropriate.
laplace(exp(-3*t))
ans =
You should see that both will be capable of computing the convolution of two signals, represented as functions. The Laplace transform applies to a convolution integral, a z transform to a discrete signal. My guess is, if you already did it using conv, then you would be intended to use a z-transform. (Hint.)
