4 plus 12 times (X-Y) plus the square of 9 (X-Y)

4 plus 12 times (X-Y) plus the square of 9 (X-Y)

solution
4+12×(x-y)+9(x-y)^2
=2^2+2×2×3(x-y)+[3(x-y)]^2
=[2+3(x-y)]^2
=(3x-3y+2)^2