Question

按某種標(biāo)準(zhǔn)，單項(xiàng)式5x²y和多項(xiàng)式a²b+2ab²-5屬于同一類，則下列哪一個(gè)多項(xiàng)式也屬于此類

1. A.
   3x³+2xy⁴
2. B.
   x²-2
3. C.
   abc-1
4. D.
   m²+2mn+n²

Answer 1

C
分析：觀察單項(xiàng)式5x²y和多項(xiàng)式a²b+2ab²-5，發(fā)現(xiàn)它們的次數(shù)都是3次，因此可以屬于同一類，然后找出四個(gè)選項(xiàng)中的三次多項(xiàng)式即可．
解答：∵單項(xiàng)式5x²y和多項(xiàng)式a²b+2ab²-5的次數(shù)都是3次，
又∵多項(xiàng)式3x³+2xy⁴的次數(shù)為4；x²-2的次數(shù)為2；abc-1的次數(shù)為3；m²+2mn+n²的次數(shù)為2；
∴多項(xiàng)式abc-1的次數(shù)與單項(xiàng)式5x²y和多項(xiàng)式a²b+2ab²-5的次數(shù)相同．
故選C．
點(diǎn)評(píng)：本題主要考查了單項(xiàng)式、多項(xiàng)式的次數(shù)的定義．能夠通過觀察發(fā)現(xiàn)單項(xiàng)式5x²y和多項(xiàng)式a²b+2ab²-5的次數(shù)相同是解題的關(guān)鍵．
單項(xiàng)式中的數(shù)字因數(shù)叫做單項(xiàng)式的系數(shù)；多項(xiàng)式中次數(shù)最高的項(xiàng)的次數(shù)叫做多項(xiàng)式的次數(shù)．