【6x^4+(x^3-y)^2-(x^3+y)^2】÷(-2x)^3
=[6x^4+x^6-2x³y+y²-x^6-2x³y-y²]÷﹙-8x³﹚
=(6x^4-4x³y﹚÷﹙-8x³﹚
=-3/4x+1/2y
=-1/4(3x-2y)
=1/4×5
=-5/4
【6x^4+(x^3-y)^2-(x^3+y)^2】÷(-2x)^3
=[6x^4+x^6-2x³y+y²-x^6-2x³y-y²]÷﹙-8x³﹚
=(6x^4-4x³y﹚÷﹙-8x³﹚
=-3/4x+1/2y
=-1/4(3x-2y)
=1/4×5
=-5/4