Question

合并多項(xiàng)式7x²y-21x²y的結(jié)果是（　�。�

A．14x²y

B．-14x⁴y²

C．-14x²y

D．-14

Answer 1

分析：原式利用合并同類項(xiàng)法則計(jì)算即可得到結(jié)果．

解答：解：7x²y-21x²y=（7-21）x²y=-14x²y．
故選C．

點(diǎn)評(píng)：此題考查了合并同類項(xiàng)，熟練掌握合并同類項(xiàng)法則是解本題的關(guān)鍵．