=-4x8x2.5x125(几个不等于零的数相乘,积的符号由负因数的个数决定.当负因数有奇数个数,积为负;当负因数的个数为偶数个时,积为正.)
=-4x2.5x8x125( 乘法交换率)
=-(4x2.5)x(8x125)(乘法结合律 )