Question

17、若干個(gè)有理數(shù)相乘，其積是負(fù)數(shù)，則負(fù)因數(shù)的個(gè)數(shù)是

奇數(shù)

．

Answer 1

分析：根據(jù)有理數(shù)的乘法的符號(hào)法則進(jìn)行判斷．

解答：解：由幾個(gè)不為零的有理數(shù)相乘的法則可知，當(dāng)負(fù)因數(shù)有奇數(shù)個(gè)時(shí)，積為負(fù)．
例如：（-1）×（-2）×（-3）×4=-24，有3個(gè)負(fù)因數(shù)，其積為負(fù)數(shù)．

點(diǎn)評(píng)：本題考查了有理數(shù)的乘法法則：幾個(gè)不等于0的數(shù)相乘，積的符號(hào)由負(fù)因數(shù)的個(gè)數(shù)決定．當(dāng)負(fù)因數(shù)有奇數(shù)個(gè)時(shí)，積為負(fù)；當(dāng)負(fù)因數(shù)有偶數(shù)個(gè)時(shí)，積為正．