2x的4次幂-3(1-2x的2次幂)(2x的2次幂+1)= (2x)^4-3(1-x^2)(2x^2+1)= (2x)^4-3(1-2x^2)(1+2x^2)
= (2x)^4-3{1-[(2x)^2]^2}=(2x)^4-3-3(2x)^4=-3-(2x)^4