（1）很抱歉·,我看不清上面平方的数字,我眼睛不太好
(2) (x-1/2)(2x+1)(2x^2+1/2)(4x^4+1/4)(16x^8+1/16)÷（256x^16+1/256)
= (X-1/2)(2X+1)(2X^2+1/2)(4X^4+1/4)(16X^8+1/16)÷[(16X^8)^2-(1/16)^2]
= (X-1/2)(2X+1)(2X^2+1/2)(4X^4+1/4)(16X^8+1/16)÷[ (16X^8-1/16)*(16X^8+1/16)]
= (X-1/2)(2X+1)(2X^2+1/2)(4X^4+1/4)÷ [(4X^4）^2-(1/4)^2]
= (X-1/2)(2X+1)(2X^2+1/2)÷(4x^4-1/4)
=(X-1/2)(2X+1)÷(2x^2-1/2)
=(2X^2-1/2)÷(2x^2-1/2)
=1
(3) [-1/6x^(2n+1)y^(2n+1)+1/3x(2n+1)y^(2n-1)+1/2x^(2n-1)y^(2n-1)]÷(-1/12x^(2n-1)y(2n-1)
=-1/6x^(2n-1)y^(2n-1)[x^2y^2+2x^2+3x^(2n-1)]/[-1/12x^(2n-1)y^(2n-1)]
=2(x^2y^2-2x^2-3)
