原式=（x+1)/x*4x²/(x+1)²--(x+1-x+1)/(x+1)(x-1)
=4x/(x+1)-2/(x+1)(x-1)
=(4x²-4x-2)/(x²-1)计算：（2y分之x）² ×2x分之y - y²分之x ÷ x分之2y²