If the square of | a + 2 | + (B-3) is 0, find the value of 3ab-4b (square)

If the square of | a + 2 | + (B-3) is 0, find the value of 3ab-4b (square)

|A + 2 | and (B-3) ^ 2 are numbers > = 0, so only
A = - 2, B = 3
3ab-4b^2=-54