答案是1/5.
原式=1/2×2/3×3/4×4/5=1/5
二[(一2)X(一4)]x3二(一8)x3二24
(2x-1)^2-x(x+4)+(x-2)(x+2) =4x2-4x+1-x2-4x+x2-4 =4x2-8x-3 =4x2-8x-4+1 =2(2x2-2x-1)+1 =2*0+1 =1
