Answer
$-27-12i$
Work Step by Step
We start with the given expression: $3i(-4+9i)$
We use the distributive property to multiply: $-4(3i)+(9i)(3i)$
We multiply the real and imaginary terms: $-12i+27i^2$
Since $i^2$ is equal to $-1$, we simplify the expression as follows: $27(-1)-12i=-27-12i$