已知数列{xn}满足x1=3,x2=x1/2,...,xn=1/2(xn-1+xn-2),n=3,4,...,则xn等于

以下用^b表示b次方.x(n) = (x(n-1) + x(n-2)) /2,两边减x(n-1)得x(n) - x(n-1) = (x(n-1) - x(n-2)) * (-1/2)所以{ x(n) - x(n-1) }是以x(2)-x(1)为首项,以-1/2为公比的等比数列所以x(n) - x(n-1) = (x(2)-x(1)) * (...