y = [√(x+1) - 1]/x= √(x+1)/x - 1/xdy/dx = [x/2√(x+1) - √(x+1)]/x² + 1/x²= -(x+2)/[2x²√(x+1)] + 1/x²当 x=8dy/dx = -10/[2×64×3] + 1/64 = -1/96