16x^2+1
16x^2 =(4X)^2
1=1^2
(4X+1)^2=16x^2+8x+1
(4X-1)^2=16x^2-8x+1
(8x²+1)²=64x^4+16x^2+1
所以单项式是8x或者是-8x或64x^4