（x-1/2）（2x²+1/2）=1/4*2（x-1/2）*2（2x²+1/2）=1/4(2x-1)(4x²+1)所以原式=1/4*(2x-1)(2x+1)/(4x²+1)/(16x^4-1)=1/4*(4x²-1)/(4x²+1)/(16x^4-1)=1/4*(16x^4-1)/(16x^4-1)=1/4
