①³√8/27-³√0.027+（-³√1/2）³
=2/3-0.3-1/2
=2/3-3/10-1/2
=-2/15
②√2又41/64+√0.81×36+1/2√0.25
=13/8+0.9×6+1/1
=13/8+5又2/5+1
=8又1/40
③（-2x）²+（6x³-12x^4）÷（3x²）
=4x^2+2x-4x^2
=2x
④a^12÷（a^8÷a²）×a³
=a^12÷a^6×a³
=a^9