题目
4x²y-1/2{x²y-[5x²y-2(2xy²+1/4xy)]}+3xy²,其中x=2,y=-3
提问时间:2020-10-19
答案
4x²y-1/2{x²y-[5x²y-2(2xy²+1/4xy)]}+3xy²
=4x²y-1/2{x²y-[5x²y-4xy²-1/2xy]}+3xy²
=4x²y-1/2{x²y-5x²y+4xy²+1/2xy}+3xy²
=4x²y-1/2{-4x²y-4xy²-1/2xy}+3xy²
=4x²y+2x²y+2xy²+1/4xy+3xy²
=6x²y+5xy²+1/4xy
=xy(6x+5y+1/4)
=-2×3×(6×2-5×3+1/4)
=-6×(-11/4)
=16.5
=4x²y-1/2{x²y-[5x²y-4xy²-1/2xy]}+3xy²
=4x²y-1/2{x²y-5x²y+4xy²+1/2xy}+3xy²
=4x²y-1/2{-4x²y-4xy²-1/2xy}+3xy²
=4x²y+2x²y+2xy²+1/4xy+3xy²
=6x²y+5xy²+1/4xy
=xy(6x+5y+1/4)
=-2×3×(6×2-5×3+1/4)
=-6×(-11/4)
=16.5
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