Question

先化简，再求值(2x-6)/(4-4x+x^2)÷ (x+3)× (x^2+x-6）/(3-x),其中x=-1/2

Answer 1

原式=2(x-3)/(x-2)²×1/(x+3)×(x-2)(x+3)/[-(x-3)]
=-2/(x-2)
当x=-1/2时
原式=-2/（-5/2）
=4/5

Answer 2

原式=2(x-3)/(x-2)²×1/(x+3)×(x-2)(x+3)/[-(x-3)]
=-2/(x-2)
当x=-1/2时
原式=-2/（-5/2）
=4/5

Answer 3

原式=2(x-3)/(x-2)^2*1/(x+3)*(x+3)(x-2)/(3-x)
=2/(2-x)
当x=-1/2时。
原式=4/5

Answer 4

(2X-6)／（4-4X+X2）×1/（X+3）×(X2+X-6)/(3-X)=-2(X-3)/(X-2)2×1/(X+3) ×(X-2)(X+3)/(X-3)=-2/(X-2),已知X=-1/2，则得4/5。