当x=2,y=-4时,
ax的3次方+1/2by+5=8a-2b+5=1999,
所以8a-2b=1994,4a-b=997,
当x=-4,y=-1/2时,
3ax-24by的3次方+4995=-12a+3b+4995
=-3(4a-b)+4995
=-3×997+4995
=-2991+4995=2004.
当x=2,y=-4时,
ax的3次方+1/2by+5=8a-2b+5=1999,
所以8a-2b=1994,4a-b=997,
当x=-4,y=-1/2时,
3ax-24by的3次方+4995=-12a+3b+4995
=-3(4a-b)+4995
=-3×997+4995
=-2991+4995=2004.