Analyzing Causality of y(n)=a^(|n|)

[Natalie89]

Homework Statement

Determine if y(n)=a^(|n|) is causal

Homework Equations

A system is causal if the output taken at anytime depends only on present and past inputs.

The Attempt at a Solution

I think the system is causal because the exponent, |n|, would represent a present value of 'n', but would this be the case when taking the magnitude of a value?

 

[╔(σ_σ)╝]

What if n=-2 ? |-2|=2 .

Thus,the system at n=-2 depends on a future value.

 

[Natalie89]

Thank you!