Question

下列說(shuō)法中，正確的是

1. A.
   單項(xiàng)式x的系數(shù)是0，次數(shù)是0
2. B.
   單項(xiàng)式-3a的系數(shù)是-3，次數(shù)是0
3. C.
   單項(xiàng)式-3×10²a²b³的系數(shù)是-3，次數(shù)是7
4. D.
   單項(xiàng)式-7x²y²的系數(shù)是-7，次數(shù)是4

Answer 1

D
分析：根據(jù)單項(xiàng)式系數(shù)和次數(shù)的解答即可，單項(xiàng)式中的數(shù)字因數(shù)是單項(xiàng)式的系數(shù)，單項(xiàng)式中所有字母的指數(shù)和是單項(xiàng)式的次數(shù)．
解答：A、單項(xiàng)式x的系數(shù)是1，次數(shù)是1；故A錯(cuò)誤．
B、單項(xiàng)式-3a的系數(shù)是-3，次數(shù)是1；故B錯(cuò)誤．
C、單項(xiàng)式-3×10²a²b³的系數(shù)是-3×10²，次數(shù)是5；故C錯(cuò)誤．
D、單項(xiàng)式-7x²y²的系數(shù)是-7，次數(shù)是4；故D正確．
故選D．
點(diǎn)評(píng)：確定單項(xiàng)式的系數(shù)和次數(shù)時(shí)，把一個(gè)單項(xiàng)式分解成數(shù)字因數(shù)和字母因式的積，是找準(zhǔn)單項(xiàng)式的系數(shù)和次數(shù)的關(guān)鍵．