3(x-y)^2[-4/15(y-x)^3][-3/2(x-y)^4]
=3(x-y)^2[4/15(x-y)^3][-3/2(x-y)^4]
=(-3×4/15×3/2)(x-y)^(2+3+4)
=-6/5 (x-y)^9