3x平方-5x平方y-{2x平方y+6xy平方-[2xy平方-3x平方y+(3x平方y-4xy平方】}
问题描述：
3x平方-5x平方y-{2x平方y+6xy平方-[2xy平方-3x平方y+(3x平方y-4xy平方】}
答
3x²-5x²y-{2x²y+6xy²-[2xy²-3x²y+(3x²y-4xy²]}
=3x²-5x²y-{2x²y+6xy²-[2xy²-3x²y+3x²y-4xy²]}
=3x²-5x²y-{2x²y+6xy²+2xy²}
=3x²-5x²y-{2x²y+8xy²}
=3x²-5x²y-2x²y-8xy²
=3x²-7x²y-8xy²