If Y is a random variable with probability mass function: 

```
 Y | Pr(Y = y)
-1 | 0.4
 0 | 0.5
 1 | 0.1

```

I need to find the standard deviation of $Z = 9 - 3Y^3$.

Approach: since it's the variance I know that 9 should not affect it and I essentially have $3^2 Var(Y^3)$ using one of the identities. My understanding is that I should be able to use the delta method to find $Var(Y^3)$ but I am not sure how. I don't think I can directly use the identity $Var(X) = E[X^2] - E[X]^2$ can I?