- #1

Quincy

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## Homework Statement

For each of the following systems, determine whether or not the system is linear, time-invariant, and causal.

a) y[n] = x[n]cos(0.2*PI*n)

b) y[n] = x[n] - x[n-1]

c) y[n] = |x[n]|

d) y[n] = Ax[n] + B, where A & B are constants.

## Homework Equations

## The Attempt at a Solution

I know that they're all causal, because they all depend on present or past values of n, I don't know how to determine if they're linear and time-invariant, the book is terrible at explaining it.