计算: (2a²+3a-1)-4(a²-a+1) 先化简,再求值: 5ab-2[3ab-(4ab²

问题描述:

计算: (2a²+3a-1)-4(a²-a+1) 先化简,再求值: 5ab-2[3ab-(4ab²
计算:
(2a²+3a-1)-4(a²-a+1)
先化简,再求值:
5ab-2[3ab-(4ab²+1/2ab)]-5ab²,其中a=1/2,b=-2/3