單項(xiàng) -

多項(xiàng) 2
分析:根據(jù)單項(xiàng)式和多項(xiàng)式的性質(zhì)進(jìn)行解答.
解答:-

只有一項(xiàng),故為單項(xiàng)式,其系數(shù)為-

,3x
2+2x-y
2共有三個單項(xiàng)式故為多項(xiàng)式,在三個單項(xiàng)式中未知數(shù)的最高次數(shù)為2,所以該多項(xiàng)式的次數(shù)為2.
點(diǎn)評:本題重點(diǎn)在于對單項(xiàng)式的系數(shù)和多項(xiàng)式的系數(shù)及次數(shù)的考查.
(1)單項(xiàng)式的表示形式:1、數(shù)與字母的乘積這樣的代數(shù)式叫做單項(xiàng)式;2、單個字母也是單項(xiàng)式.3、單個的數(shù)是單項(xiàng)式;4、字母與字母相乘成為單項(xiàng)式;5、數(shù)與數(shù)相乘稱為單項(xiàng)式.(2)單項(xiàng)式的系數(shù):單項(xiàng)式中的數(shù)字因數(shù)及性質(zhì)符號叫做單項(xiàng)式的系數(shù).
(3)幾個單項(xiàng)式的和叫做多項(xiàng)式.在多項(xiàng)式中,每個單項(xiàng)式叫做多項(xiàng)式的項(xiàng),其中不含字母的項(xiàng)叫做常數(shù)項(xiàng).一個多項(xiàng)式有幾項(xiàng)就叫做幾項(xiàng)式
(4)多項(xiàng)式中,次數(shù)最高的項(xiàng)的次數(shù),就是這個多項(xiàng)式的次數(shù).