2x²(x²-1/2x+1)-x(2x³-x³+3x-1),其中x=-1/2(2)3x-(x²-2x+1-2x²(x-3) (-1/2ab)(2/3ab²-2ab+4/3b+1)(-1/2ab)(2/3ab²-2ab+4/3b+1) 是第三题

问题描述:

2x²(x²-1/2x+1)-x(2x³-x³+3x-1),其中x=-1/2
(2)3x-(x²-2x+1-2x²(x-3) (-1/2ab)(2/3ab²-2ab+4/3b+1)
(-1/2ab)(2/3ab²-2ab+4/3b+1) 是第三题

此类问题的通解是
先化简,再求值.先按乘法分配率去掉括号,再按降幂逐项合并,最后代入数值求解.