求多项式的值,3abc-5的2次方b+[abc-（4ab的2次方-3a的2次方b]?其中a=-2,b=-1,c=1/4?一共两个算式
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3abc - 5a²b + [ abc - (4ab² - 3a²b)]
= 3abc - 5a²b + abc - 4ab² + 3a²b
= 4abc - 2a²b - 4ab²
= 2ab(2c - a - 2b)
= 2×(-2)×(-1)×[2×1/4 - (-2) - 2×(-1)]
= 4×(1/2 +2 +2)
= 4× 9/2
= 18