x-2分之4x-x的平方除(x+2减去 x-2分之12),其中x=-二分之一,化简求值
问题描述：
x-2分之4x-x的平方除(x+2减去 x-2分之12),其中x=-二分之一,化简求值
答
(4x-x²)/(x-2)÷[x+2-12/(x-2)]
=-x(x-4)/(x-2)÷[(x+2)(x-2)-12]/(x-2)
=-x(x-4)/(x-2)÷(x²-4-12)/(x-2)
=-x(x-4)/(x-2)÷(x+4)(x-4)/(x-2)
=-x(x-4)/(x-2)×(x-2)/(x+4)(x-4)
=-x/(x+4)
=-(-1/2)/(-1/2+4)
=(1/2)/(7/2)
=1/7